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dcastlen50
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Reconstructed discussion whether belief in literal Adam & Eve is warranted
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What usually happens: catagorize items, data; measure, weigh, compare, determine probabilities of events etc
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Dr.Bonnette
Guest
Some philosophical reflections pertinent to Adam and Eve:
The purpose of this post is not to open lengthy debate about the details or credibility of certain foundational themes of Christian philosophy, but rather to examine questions that are more specifically relevant to Adam and Eve’s existence. Those who reject these basic claims may do so, but for Christian philosophers, these are some of the logical presuppositions which help render reasonable belief in a literal Adam and Eve.
First, God exists, and can therefore play a special role in Adam’s creation as well as in human history. Christian philosophy maintains (in accord with Catholic teaching) that God’s existence can be known by the light of natural reason. Major Christian thinkers (also some pagans) down through history – scholars well aware of the distinction between theology and philosophy – have defended philosophical proofs for God’s existence. The fact that atheists and fideists reject these proofs is hardly news. While it is perfectly legitimate to criticize and debate whether God’s existence can be proven, that project would be a sure recipe for endless digression, never getting around to dealing with topics more specific to Adam and Eve.
Second, man possesses a spiritual and immortal soul, which God alone can create. Christian philosophers maintain that God has created some sort of special nature in man, a nature distinguished by intellective and volitional activities that separate him essentially from the rest of the animal kingdom. Again, both pagan and Christian thinkers have reached similar conclusions for purely philosophical reasons. These conclusions again could be debated endlessly. But I suspect most readers here would rather know whether this claim makes any sense in terms of what we know of human origins from natural science.
The difficulty raised by natural science appears to be that the paleological record does not seem to fit with the notion of a single first man, somehow instantly essentially superior to all previous lower animals, especially to subhuman primates. The reason for this objection is what appears to be the very gradual changes in tool-making ability and other behaviors of primates over great spans of time, all of which argue against the sudden appearance of a first true human being, or beings, who are essentially superior to prior primates.
Philosophical concepts essential to this claim are that true man possesses a substantial form, which unifies, specifies, and makes actual the presence of the intellective, volitional, spiritual person of an animate nature – and that this qualitatively superior step in nature and being is such that it represents a line of demarcation which is not amenable to gradual development. Materialistic evolutionists claim otherwise, saying that the record of change is slow, with gradual increases in cranial capacity, tool-making abilities, acquisition of controlled use of fire, and so forth. In a way, it seems odd that the simple claim that man has a special nature should be so controversial – but that is the sticking point for evolutionary materialists, who insist that there is no special human nature, and that man is simply the end population stages of a gradual development of purely animal organisms over millions of year. To them, man is just a highly developed animal. To Christian philosophers, man is an essentially distinct natural philosophical species, possessing a spiritual soul, with intellect and will not shared by brute animals.
How is it possible to explain the physical record of gradual primate anatomical and artifact development while claiming that there is an Adam, who is the first true man, essentially superior to all of his predecessors? Most evolutionists declare that there could have been no “Adam.”
Viewed purely as a material being, man does appear as merely the end product of billions of years of biological rearrangements of chemical constituents. When an atom of sodium and one of chlorine unite to form a molecule of salt, one can look at this union as merely the “hand-shaking” of two distinct atoms, the mere “donation” of one electron from the chlorine to the sodium atom. So, too, as chemical complexity increases over eons, organisms resulting from evolutionary mechanisms can be viewed as merely highly-complex “chemical soups” in a temporary state of equilibrium, but not as things in themselves, possessing some real unifying principle beyond the general laws of physics and chemistry which govern all material entities. In crude terms, it comes down to asking whether we are merely a more or less attractive-looking pile of atoms with a name attached, or are we really one being with a common human nature throughout. To save common sense, which tells us that we are real things, substantially one in nature throughout our entire bodily being, Christian philosophy maintains that an essential unifying principle, the substantial form, actualizes matter, specifying it as being of a stable human nature. This human nature is essentially distinct from and superior to the nature of subhuman primates and other lower animals. In man, the substantial form determines all the powers we possess, including those of intellect and free will, which latter set us apart from, and ontologically above, brute animals. This same substantial form (soul) determines that we are a person, spiritual in form and with personal immortality. Since we then possess a spiritual soul, and since spirit cannot come from matter, God alone can create each and every human spiritual soul.
Continued…
The purpose of this post is not to open lengthy debate about the details or credibility of certain foundational themes of Christian philosophy, but rather to examine questions that are more specifically relevant to Adam and Eve’s existence. Those who reject these basic claims may do so, but for Christian philosophers, these are some of the logical presuppositions which help render reasonable belief in a literal Adam and Eve.
First, God exists, and can therefore play a special role in Adam’s creation as well as in human history. Christian philosophy maintains (in accord with Catholic teaching) that God’s existence can be known by the light of natural reason. Major Christian thinkers (also some pagans) down through history – scholars well aware of the distinction between theology and philosophy – have defended philosophical proofs for God’s existence. The fact that atheists and fideists reject these proofs is hardly news. While it is perfectly legitimate to criticize and debate whether God’s existence can be proven, that project would be a sure recipe for endless digression, never getting around to dealing with topics more specific to Adam and Eve.
Second, man possesses a spiritual and immortal soul, which God alone can create. Christian philosophers maintain that God has created some sort of special nature in man, a nature distinguished by intellective and volitional activities that separate him essentially from the rest of the animal kingdom. Again, both pagan and Christian thinkers have reached similar conclusions for purely philosophical reasons. These conclusions again could be debated endlessly. But I suspect most readers here would rather know whether this claim makes any sense in terms of what we know of human origins from natural science.
The difficulty raised by natural science appears to be that the paleological record does not seem to fit with the notion of a single first man, somehow instantly essentially superior to all previous lower animals, especially to subhuman primates. The reason for this objection is what appears to be the very gradual changes in tool-making ability and other behaviors of primates over great spans of time, all of which argue against the sudden appearance of a first true human being, or beings, who are essentially superior to prior primates.
Philosophical concepts essential to this claim are that true man possesses a substantial form, which unifies, specifies, and makes actual the presence of the intellective, volitional, spiritual person of an animate nature – and that this qualitatively superior step in nature and being is such that it represents a line of demarcation which is not amenable to gradual development. Materialistic evolutionists claim otherwise, saying that the record of change is slow, with gradual increases in cranial capacity, tool-making abilities, acquisition of controlled use of fire, and so forth. In a way, it seems odd that the simple claim that man has a special nature should be so controversial – but that is the sticking point for evolutionary materialists, who insist that there is no special human nature, and that man is simply the end population stages of a gradual development of purely animal organisms over millions of year. To them, man is just a highly developed animal. To Christian philosophers, man is an essentially distinct natural philosophical species, possessing a spiritual soul, with intellect and will not shared by brute animals.
How is it possible to explain the physical record of gradual primate anatomical and artifact development while claiming that there is an Adam, who is the first true man, essentially superior to all of his predecessors? Most evolutionists declare that there could have been no “Adam.”
Viewed purely as a material being, man does appear as merely the end product of billions of years of biological rearrangements of chemical constituents. When an atom of sodium and one of chlorine unite to form a molecule of salt, one can look at this union as merely the “hand-shaking” of two distinct atoms, the mere “donation” of one electron from the chlorine to the sodium atom. So, too, as chemical complexity increases over eons, organisms resulting from evolutionary mechanisms can be viewed as merely highly-complex “chemical soups” in a temporary state of equilibrium, but not as things in themselves, possessing some real unifying principle beyond the general laws of physics and chemistry which govern all material entities. In crude terms, it comes down to asking whether we are merely a more or less attractive-looking pile of atoms with a name attached, or are we really one being with a common human nature throughout. To save common sense, which tells us that we are real things, substantially one in nature throughout our entire bodily being, Christian philosophy maintains that an essential unifying principle, the substantial form, actualizes matter, specifying it as being of a stable human nature. This human nature is essentially distinct from and superior to the nature of subhuman primates and other lower animals. In man, the substantial form determines all the powers we possess, including those of intellect and free will, which latter set us apart from, and ontologically above, brute animals. This same substantial form (soul) determines that we are a person, spiritual in form and with personal immortality. Since we then possess a spiritual soul, and since spirit cannot come from matter, God alone can create each and every human spiritual soul.
Continued…
D
Dr.Bonnette
Guest
Continued…
Hence, the first human being created by God, whatever the circumstances, would be Adam. Since a being must be either spiritual in nature, or not, there is no possibility of gradual attainment of a spiritual soul. The first human being would be completely human, with all prior primates being merely subhuman, material organisms. Prior primates would have sense powers, but man alone would have the spiritual faculties of intellect and free will.
This scenario, as depicted by Christian philosophy, does not violate the data of natural science, because the possession of spiritual faculties does not mean that they must always be in act. We can detect their presence by finding signs of intellective activity in forms of special types of tool making or art or cultural rituals. But the absence of such signs does not assure us of the absence of intellect, since man can also engage in the same activities as mere animals and/or material signs of his intellective activity may be obliterated by the ravages of time. The fact that gradual improvement in tool making or other activities takes place over time does not prove that a radical line of demarcation is not present. At some point in time, true man became present. Before that he was not, and what we find are simply signs of complex sentient behaviors of lower animals, including subhuman primates.
The evidence of this line of demarcation lies in the same evidence Christian philosophers use to prove that man is essentially superior to brute animals today, that his soul is spiritual and theirs is not. If the distinction exists today, it must have begun to exist at some time in the past, since true man was not always in existence. Thus some first presence must have occurred, and the first human being having such faculties was therefore he who we call Adam.
Objections that not all men exhibit full intellective powers at all times – or in some instances, not at all – are not valid. The nature is stable in this type of being, whether he acts fully in accord with it or not. When we are sleeping or comatose, we may not be thinking or playing the piano, but we remain fully human. The nature belongs to the human natural species, whether it is fully operative at all times or any time at all. (This is the philosophical distinction between possession of an operative potency, or power, and its actuation. Actuation is not always possible, either because we are performing a contrary act or because of defect in the organs needed for operation, as in the case of brain disease or malformation.)
I realize that a materialist will have none of this, since he denies that man possesses any spiritual powers at all, and claims that all animal activity, including human, is basically dependent upon brain activity and other physically organic functions. I am not arguing that point here, since a materialist would deny all the basic presuppositions of the type of worldview in which the question of Adam and Eve arises anyway. What I am saying is that Christian philosophy provides a structure in which the belief in Adam and Eve makes sense, given the foundational system in which the question reasonably arises. That is, if you grant the existence of God and the spirituality of the human soul, then God must have created a first human being at some point in the evolution of earth’s history – and that first human being would be he who believers call Adam. Moreover, I am saying that the structure of Christian philosophy can reasonably adapt to the evidence of natural science which points to gradual development of behaviors, from the purely sensory to the clearly intellective. Materialists understandably read the same data entirely otherwise, but that reflects a radically distinct philosophical worldview from the one in which the question of Adam and Eve’s literal existence would be expected to arise. Thus, for Christians, belief in a literal Adam and Eve is warranted in the sense (1) that it does not violate their general philosophical worldview, (2) that that worldview is not inconsistent with what we know of primate and human development over time, and (3) that the arguments for the human spiritual nature necessarily imply some first true human being, whom we call Adam.
Hence, the first human being created by God, whatever the circumstances, would be Adam. Since a being must be either spiritual in nature, or not, there is no possibility of gradual attainment of a spiritual soul. The first human being would be completely human, with all prior primates being merely subhuman, material organisms. Prior primates would have sense powers, but man alone would have the spiritual faculties of intellect and free will.
This scenario, as depicted by Christian philosophy, does not violate the data of natural science, because the possession of spiritual faculties does not mean that they must always be in act. We can detect their presence by finding signs of intellective activity in forms of special types of tool making or art or cultural rituals. But the absence of such signs does not assure us of the absence of intellect, since man can also engage in the same activities as mere animals and/or material signs of his intellective activity may be obliterated by the ravages of time. The fact that gradual improvement in tool making or other activities takes place over time does not prove that a radical line of demarcation is not present. At some point in time, true man became present. Before that he was not, and what we find are simply signs of complex sentient behaviors of lower animals, including subhuman primates.
The evidence of this line of demarcation lies in the same evidence Christian philosophers use to prove that man is essentially superior to brute animals today, that his soul is spiritual and theirs is not. If the distinction exists today, it must have begun to exist at some time in the past, since true man was not always in existence. Thus some first presence must have occurred, and the first human being having such faculties was therefore he who we call Adam.
Objections that not all men exhibit full intellective powers at all times – or in some instances, not at all – are not valid. The nature is stable in this type of being, whether he acts fully in accord with it or not. When we are sleeping or comatose, we may not be thinking or playing the piano, but we remain fully human. The nature belongs to the human natural species, whether it is fully operative at all times or any time at all. (This is the philosophical distinction between possession of an operative potency, or power, and its actuation. Actuation is not always possible, either because we are performing a contrary act or because of defect in the organs needed for operation, as in the case of brain disease or malformation.)
I realize that a materialist will have none of this, since he denies that man possesses any spiritual powers at all, and claims that all animal activity, including human, is basically dependent upon brain activity and other physically organic functions. I am not arguing that point here, since a materialist would deny all the basic presuppositions of the type of worldview in which the question of Adam and Eve arises anyway. What I am saying is that Christian philosophy provides a structure in which the belief in Adam and Eve makes sense, given the foundational system in which the question reasonably arises. That is, if you grant the existence of God and the spirituality of the human soul, then God must have created a first human being at some point in the evolution of earth’s history – and that first human being would be he who believers call Adam. Moreover, I am saying that the structure of Christian philosophy can reasonably adapt to the evidence of natural science which points to gradual development of behaviors, from the purely sensory to the clearly intellective. Materialists understandably read the same data entirely otherwise, but that reflects a radically distinct philosophical worldview from the one in which the question of Adam and Eve’s literal existence would be expected to arise. Thus, for Christians, belief in a literal Adam and Eve is warranted in the sense (1) that it does not violate their general philosophical worldview, (2) that that worldview is not inconsistent with what we know of primate and human development over time, and (3) that the arguments for the human spiritual nature necessarily imply some first true human being, whom we call Adam.
A
anthony022071
Guest
Having a temporal life and having a morally conscious life are two different things.No, I haven’t forgotten that. I merely pointed out that more than half of humanity never experiences temporal life.
Unborn persons do have a temporal life,just not out of the womb.
S
StAnastasia
Guest
Of course. The relevant point is that for possibly billions of people they have no experience of their temporal life. They undergo spontaneous abortion within hours or days of conception.Having a temporal life and having a morally conscious life are two different things…
A
anthony022071
Guest
They die a natural death.Of course. The relevant point is that for possibly billions of people they have no experience of their temporal life. They undergo spontaneous abortion within hours or days of conception.
D
Dr.Bonnette
Guest
To hecd2 re posts 220, 221, 222, and 223:
Alec,
In these posts, you have powerfully defended your thesis that there have been no bottlenecks of just two people in millions of years. A good example of the kind of argument you offer is the following: *"… the assertion that the molecular data is consistent with a bottleneck of two is just that - an assertion completely unsupported by the evidence - in fact denied by it because the DRB1 data on its own logically precludes such an extreme bottleneck and that is before we consider the size of a real population capable of sustaining the heterozygosity, microsatellite and LD data that we see. A bottleneck of two would result in far more homozygosity than we see as neutral alleles drift to extinction or fixation rapidly in a tiny population. … To prove me wrong, all you have to do is to cite a reference to a paper which sets out the reasoning for considering a bottleneck of two as a possibility." *
I am going to concur with your claim that “…there is remarkable consistency across multiple methods of estimating palaeo-demography, and there is unanimity that the population ancestral to humans never passed through a bottleneck of two individuals…”
Nonetheless, careful reading of your posts suggests to me that your conclusion about the scientific concensus is not based on the question of effective population size, but rather on other aspects of specific genes. Regarding effective population size, you affirm that in the last million years the concensus has been that it has been about 10,000, while Tenesa puts it at 7,500 in 2007. The important point of this is that when the genome in general is considered, the long-term effective population size of either 7,500 or 10,000 is consistent with the possibility of a bottleneck of just two individuals within the past 10,000 generations or so. For example, in Wen-Hsiung Li’s widely-used textbook, Molecular Evolution, he states (pp. 46-47):
*"The effective population size can also be much reduced due to long-term variations in the population size, which in turn are caused by such factors as environmental catastrophes, cyclical modes of reproduction, and local extinction and recolonization events. For example, the long-term effective population size in a species for a period of n generations is given by:
Ne = n/(1/N1 + 1/N2 + … + !/Nn)
where Ni is the population size of the ith generation. In other words, Ne equals the harmonic mean of the Ni values, and consequently it is close to the smallest value of Ni than to the largest one. Similarly if a population goes through a bottleneck, the effective population size is greatly reduced."*
My biology contacts tell me that if one uses the formula above for the effective population size, then a population which starts with 2 individuals and expands within ten generations to 10,000 individuals and then remained constant would have an effective population size of about 6,000. If it expanded quickly from 2 to 100,000, the effective population size would be about 12,000. Thus, with the uncertainties involved, a bottleneck of two is easily compatible with the effective population size of about 10,000 today.
You write: “Furthermore, there isn’t the slightest shred of evidence to support the notion that the human population could or did expand at more than 100% per generation over ten generations in palaeolithic times.” We must always recall that absence of evidence is not the same thing as evidence of absence. I can tell you easily how the human population could have expanded more than 100% per generation over ten generations. It is simple. Start with Adam and Eve and let them have just six children, three boys and three girls. (Incest was not an initial problem.) These three pairs mate producing each six more children, equally divided by sex. That give us 18 in the next generation. These then mate to so that 9 pairs x 6 children equals 54 more people. Each generation is producing 300% more than itself! The math runs then for sequential generations: 6, 18, 54, 162, 486, 1458, 4374, 13122! Oops! That is only EIGHT generations to exceed 10,000 persons! But how could this be so perfectly “arranged” in nature? I am not saying this exact scenario occurred, but merely showing that such rapid population growth is not beyond the range of possibilities that may exist in this amazing world.
From this perspective, the effective population size of 10,000 in the last million years easily could allow a bottleneck of just two individuals, Adam and Eve, quickly propagating 10,000 individuals in just ten generations or so.
Continued…
Alec,
In these posts, you have powerfully defended your thesis that there have been no bottlenecks of just two people in millions of years. A good example of the kind of argument you offer is the following: *"… the assertion that the molecular data is consistent with a bottleneck of two is just that - an assertion completely unsupported by the evidence - in fact denied by it because the DRB1 data on its own logically precludes such an extreme bottleneck and that is before we consider the size of a real population capable of sustaining the heterozygosity, microsatellite and LD data that we see. A bottleneck of two would result in far more homozygosity than we see as neutral alleles drift to extinction or fixation rapidly in a tiny population. … To prove me wrong, all you have to do is to cite a reference to a paper which sets out the reasoning for considering a bottleneck of two as a possibility." *
I am going to concur with your claim that “…there is remarkable consistency across multiple methods of estimating palaeo-demography, and there is unanimity that the population ancestral to humans never passed through a bottleneck of two individuals…”
Nonetheless, careful reading of your posts suggests to me that your conclusion about the scientific concensus is not based on the question of effective population size, but rather on other aspects of specific genes. Regarding effective population size, you affirm that in the last million years the concensus has been that it has been about 10,000, while Tenesa puts it at 7,500 in 2007. The important point of this is that when the genome in general is considered, the long-term effective population size of either 7,500 or 10,000 is consistent with the possibility of a bottleneck of just two individuals within the past 10,000 generations or so. For example, in Wen-Hsiung Li’s widely-used textbook, Molecular Evolution, he states (pp. 46-47):
*"The effective population size can also be much reduced due to long-term variations in the population size, which in turn are caused by such factors as environmental catastrophes, cyclical modes of reproduction, and local extinction and recolonization events. For example, the long-term effective population size in a species for a period of n generations is given by:
Ne = n/(1/N1 + 1/N2 + … + !/Nn)
where Ni is the population size of the ith generation. In other words, Ne equals the harmonic mean of the Ni values, and consequently it is close to the smallest value of Ni than to the largest one. Similarly if a population goes through a bottleneck, the effective population size is greatly reduced."*
My biology contacts tell me that if one uses the formula above for the effective population size, then a population which starts with 2 individuals and expands within ten generations to 10,000 individuals and then remained constant would have an effective population size of about 6,000. If it expanded quickly from 2 to 100,000, the effective population size would be about 12,000. Thus, with the uncertainties involved, a bottleneck of two is easily compatible with the effective population size of about 10,000 today.
You write: “Furthermore, there isn’t the slightest shred of evidence to support the notion that the human population could or did expand at more than 100% per generation over ten generations in palaeolithic times.” We must always recall that absence of evidence is not the same thing as evidence of absence. I can tell you easily how the human population could have expanded more than 100% per generation over ten generations. It is simple. Start with Adam and Eve and let them have just six children, three boys and three girls. (Incest was not an initial problem.) These three pairs mate producing each six more children, equally divided by sex. That give us 18 in the next generation. These then mate to so that 9 pairs x 6 children equals 54 more people. Each generation is producing 300% more than itself! The math runs then for sequential generations: 6, 18, 54, 162, 486, 1458, 4374, 13122! Oops! That is only EIGHT generations to exceed 10,000 persons! But how could this be so perfectly “arranged” in nature? I am not saying this exact scenario occurred, but merely showing that such rapid population growth is not beyond the range of possibilities that may exist in this amazing world.
From this perspective, the effective population size of 10,000 in the last million years easily could allow a bottleneck of just two individuals, Adam and Eve, quickly propagating 10,000 individuals in just ten generations or so.
Continued…
D
Dr.Bonnette
Guest
To hecd2…continued:
So, why do your experts insist the population never could have been smaller than, say, one thousand?
Now here is where I am going to partly agree with you. You have built a powerful case to prove that other specific genes in the genome indicate in various ways that a bottleneck smaller than one thousand appears impossible. The problem with that is that specific genes might behave in unusual ways, and so are less reliable. Or, we may discover something about them we did not previously know. Consider the case of Ayala’s 1994 claims about a specific behavior in the genes. In 2006, Shiina et al., contradict his thesis about massive flow of alleles from one species to the next:
"This result finally puts the MHC in line with the bulk of population and evolutionary genetics data which firmly conclude that a narrow bottleneck has occurred at the origin of our species (Cann et al. 1987; Hammer 1995), a fact inconsistent with massive flow of alleles from one species to the next as required by the transspecies postulate (Ayala et al. 1994).” Takashi Shiina, et al. (2006) Rapid Evolution of Major Histocompatibility Complex Class I Genes in Primates Generates New Disease Alleles in Humans via Hitchhiking Diversity. Genetics, 173, 1555-1570.
The only inference I am here drawing from this more recent article is that it appears Ayala was wrong in 1994 about his “transspecies postulate.” Scientists can make mistakes, even in molecular biology. If you are making the argument that a bottleneck of two is impossible based on particular genes, that may be very impressive in terms of what we presently know about the human genome. Still, that is a very different argument than the one based on effective population size, whose conventional estimate for the last million years is quite consistent with the possibility of a bottleneck of just two. Even if we grant the force of your present arguments (and I am confident you will inundate me with much more supporting evidence and “absolute certitudes”), the difficulty is that we may find out something “surprising” about gene behavior in the future – just as we did in the case of Ayala’s 1994 claim. Moreover, there is an inherent uncertainty “built into” any attempt to determine absolute certitudes about specific distant past events based solely upon microscopic analysis of present evidence, especially when much of the science is of very recent vintage and entails many assumptions and estimates. Unlike Catholic dogma, this is not the stuff of divine revelation.
That is why in my book, Origin of the Human Species, first published in 2001, I conceded that a bottleneck of two would be considered by scientists to be improbable. Nonetheless, consider the improbability of the Big Bang’s expansion rate being so incredibly balanced that it avoided the outcome that life that would never have occurred had it been either the slightest bit greater or smaller. If I were viewing the situation as you do, without factoring in the ability of God to create the actual beginning, then I might consider that a bottleneck of two could not take place. But, I believe in (and can demonstrate philosophically) the existence of a personal God who is quite capable of exercising providence over the whole of His creation – vanquishing improbabilities, and allowing for rapid population growth from two first parents.
It has been the history of natural science to think it has had “everything figured out.” Despite the supreme confidence you exhibit in the most recent findings of molecular biology, one must balance this with some awareness of the radical tentativeness of specific theories and paradigms, even if you believe that science makes general progress. On an even larger scale, consider the overconfident mentality of scientists at the end of the 19th Century who thought that Newtonian science had triumphed over all – just before relativity theory and quantum mechanics radically undercut those expectations.
Over time, the prospects for Adam and Eve have improved on the large scale. The consensus has moved away from the idea that true humans evolved in separate parts of the globe simultaneously, which would have grossly violated the thesis of a single pair of first parents: Wolpoff’s multiregional hypothesis has given ground to more general acceptance of the single-source “out of Africa” hypothesis. And, rather than having constant expansion of an ever-growing primate population dating too far into the past for Adam and Eve, the effective population size estimates have actually dropped in size, from the 100,000 estimate for the last 30 million years to just 10,000, or even less, for the last million years – allowing at least the mathematical possibility of a bottleneck of two since the middle Pleistocene period. Potential future uncertainties cannot be ruled out at this time unless one possesses a crystal ball.
As I have indicated in other posts, although there remain some somewhat unsettled areas in the theological, philosophical, and natural scientific analyses regarding this matter, I maintain that it is reasonable for 21st Century, educated people to believe in a literal Adam and Eve.
So, why do your experts insist the population never could have been smaller than, say, one thousand?
Now here is where I am going to partly agree with you. You have built a powerful case to prove that other specific genes in the genome indicate in various ways that a bottleneck smaller than one thousand appears impossible. The problem with that is that specific genes might behave in unusual ways, and so are less reliable. Or, we may discover something about them we did not previously know. Consider the case of Ayala’s 1994 claims about a specific behavior in the genes. In 2006, Shiina et al., contradict his thesis about massive flow of alleles from one species to the next:
"This result finally puts the MHC in line with the bulk of population and evolutionary genetics data which firmly conclude that a narrow bottleneck has occurred at the origin of our species (Cann et al. 1987; Hammer 1995), a fact inconsistent with massive flow of alleles from one species to the next as required by the transspecies postulate (Ayala et al. 1994).” Takashi Shiina, et al. (2006) Rapid Evolution of Major Histocompatibility Complex Class I Genes in Primates Generates New Disease Alleles in Humans via Hitchhiking Diversity. Genetics, 173, 1555-1570.
The only inference I am here drawing from this more recent article is that it appears Ayala was wrong in 1994 about his “transspecies postulate.” Scientists can make mistakes, even in molecular biology. If you are making the argument that a bottleneck of two is impossible based on particular genes, that may be very impressive in terms of what we presently know about the human genome. Still, that is a very different argument than the one based on effective population size, whose conventional estimate for the last million years is quite consistent with the possibility of a bottleneck of just two. Even if we grant the force of your present arguments (and I am confident you will inundate me with much more supporting evidence and “absolute certitudes”), the difficulty is that we may find out something “surprising” about gene behavior in the future – just as we did in the case of Ayala’s 1994 claim. Moreover, there is an inherent uncertainty “built into” any attempt to determine absolute certitudes about specific distant past events based solely upon microscopic analysis of present evidence, especially when much of the science is of very recent vintage and entails many assumptions and estimates. Unlike Catholic dogma, this is not the stuff of divine revelation.
That is why in my book, Origin of the Human Species, first published in 2001, I conceded that a bottleneck of two would be considered by scientists to be improbable. Nonetheless, consider the improbability of the Big Bang’s expansion rate being so incredibly balanced that it avoided the outcome that life that would never have occurred had it been either the slightest bit greater or smaller. If I were viewing the situation as you do, without factoring in the ability of God to create the actual beginning, then I might consider that a bottleneck of two could not take place. But, I believe in (and can demonstrate philosophically) the existence of a personal God who is quite capable of exercising providence over the whole of His creation – vanquishing improbabilities, and allowing for rapid population growth from two first parents.
It has been the history of natural science to think it has had “everything figured out.” Despite the supreme confidence you exhibit in the most recent findings of molecular biology, one must balance this with some awareness of the radical tentativeness of specific theories and paradigms, even if you believe that science makes general progress. On an even larger scale, consider the overconfident mentality of scientists at the end of the 19th Century who thought that Newtonian science had triumphed over all – just before relativity theory and quantum mechanics radically undercut those expectations.
Over time, the prospects for Adam and Eve have improved on the large scale. The consensus has moved away from the idea that true humans evolved in separate parts of the globe simultaneously, which would have grossly violated the thesis of a single pair of first parents: Wolpoff’s multiregional hypothesis has given ground to more general acceptance of the single-source “out of Africa” hypothesis. And, rather than having constant expansion of an ever-growing primate population dating too far into the past for Adam and Eve, the effective population size estimates have actually dropped in size, from the 100,000 estimate for the last 30 million years to just 10,000, or even less, for the last million years – allowing at least the mathematical possibility of a bottleneck of two since the middle Pleistocene period. Potential future uncertainties cannot be ruled out at this time unless one possesses a crystal ball.
As I have indicated in other posts, although there remain some somewhat unsettled areas in the theological, philosophical, and natural scientific analyses regarding this matter, I maintain that it is reasonable for 21st Century, educated people to believe in a literal Adam and Eve.
S
StAnastasia
Guest
Nor is it less reasonable to believe in Pandora’s Box.I maintain that it is reasonable for 21st Century, educated people to believe in a literal Adam and Eve.
G
grannymh
Guest
Interesting response. Personally, I’ve found it reasonable to pay attention to Pandora’s Box–cuts down unnecessary hassle. I also find it reasonable to read the fine print in posts 265 & 266. Interesting points and raised questions–the kind of stuff that inspires further possibilities and fruitful investigation which, as I understand, is the goal of science. By the way, Thomas Edison and Gertrude Ederle are two of my favorite people.Nor is it less reasonable to believe in Pandora’s Box.
Blessings,
granny
Humanity is worthy of being understood.
S
StAnastasia
Guest
Interesting response. Personally, I’ve found it reasonable to pay attention to Pandora’s Box–cuts down
Nice to see you back, Granny!
A
anthony022071
Guest
The belief in Adam and Eve is warranted because the Church,which teaches this belief, was founded by Christ,and his Spirit guides the Church in the definition of its doctrines and the interpretation of scripture. The belief in the divine origin of the Church is,in turn, warranted because of the saints,whose lives are ever-present witnesses to the fact that Christ is risen from the dead and that his Spirit is present in themselves and in the Church to which they belong. The saints and the lives they lead are proof of the divine origin of the Church and the truth of its doctrines.
S
StAnastasia
Guest
The belief in “Adam” and “Eve” is also consistent with a 13.7 billion year old earth.The belief in Adam and Eve is warranted because the Church,which teaches this belief, was founded by Christ,and his Spirit guides the Church in the definition of its doctrines and the interpretation of scripture. The belief in the divine origin of the Church is,in turn, warranted because of the saints,whose lives are ever-present witnesses to the fact that Christ is risen from the dead and that his Spirit is present in themselves and in the Church to which they belong. The saints and the lives they lead are proof of the divine origin of the Church and the truth of its doctrines.
A
anthony022071
Guest
No one can measure the age of the Earth. Measurement of a distance can only be made if you are capable of reaching the limits of a distance yourself or by means of something that can be sent out to reach the other end (as with an anchor from a boat) or by estimating with reference to some point or marker whose distance is known. But it is not possible to reach past time and there is nothing to use as a reference point to estimate the age of the Earth or the universe.The belief in “Adam” and “Eve” is also consistent with a 13.7 billion year old earth.
S
StAnastasia
Guest
Not true at all.No one can measure the age of the Earth.
D
Dr.Bonnette
Guest
The question has come up about twinning and the soul. Since the best science indicates that specifically human matter is present from the moment of conception, hylemorphic doctrine (St. Thomas’ analysis) suggests that the human soul is present from that very first moment of conception. The human spiritual soul is the substantial form which places the embryo into the human species.
Now, is there one soul, or two, present in the case of twins? I would say that there is but one soul present. Upon twinning, the matter divides into two individuals, making one twin the “original” one, while God creates a second soul to animate the other one’s matter. Since the DNA, etc., is that of both the biological mother and father, the “second” twin is not the child of the first twin, but simply a sibling with shared parents.
The theological implications of the many early spontaneous abortions (miscarriages) is of great interest, of course. I have a colleague whose doctoral dissertation was on the natural state of happiness attained by these souls, even absent the theological reality of the Beatific Vision. Since the BV is a supernatural gift of God, it need not mean that natural happiness is lost by souls whose morality is never tested by life experience. Of course, baptized infants obtain the BV through no merit of their own, but rather through what is essentially the free gift of God.
Injustice is done in neither case, since the individual has done nothing himself to merit eternal happiness, and in both cases happiness is attained – though in hugely greater measure through the BV.
Now, is there one soul, or two, present in the case of twins? I would say that there is but one soul present. Upon twinning, the matter divides into two individuals, making one twin the “original” one, while God creates a second soul to animate the other one’s matter. Since the DNA, etc., is that of both the biological mother and father, the “second” twin is not the child of the first twin, but simply a sibling with shared parents.
The theological implications of the many early spontaneous abortions (miscarriages) is of great interest, of course. I have a colleague whose doctoral dissertation was on the natural state of happiness attained by these souls, even absent the theological reality of the Beatific Vision. Since the BV is a supernatural gift of God, it need not mean that natural happiness is lost by souls whose morality is never tested by life experience. Of course, baptized infants obtain the BV through no merit of their own, but rather through what is essentially the free gift of God.
Injustice is done in neither case, since the individual has done nothing himself to merit eternal happiness, and in both cases happiness is attained – though in hugely greater measure through the BV.
A
anthony022071
Guest
The soul is the form of the body,and it is the life of the body. Two individual persons cannot be one and the same form or life.Now, is there one soul, or two, present in the case of twins? I would say that there is but one soul present. Upon twinning, the matter divides into two individuals, making one twin the “original” one, while God creates a second soul to animate the other one’s matter. Since the DNA, etc., is that of both the biological mother and father, the “second” twin is not the child of the first twin, but simply a sibling with shared parents.
H
hecd2
Guest
In your posts 260, 261, 265 and 266 you set out your arguments in support of your position that belief in a literal Adam and Eve is warranted. In this, and subsequent posts, I intend to show why such a belief is unwarranted if one applies the standards of a well and broadly educated reasonable person. In your posts you make much of the claim that belief in a literal Adam and Eve is warranted in the context of Christian philosophy. This is not a valid argument on its own for assenting to a proposition about human origins that is amenable to investigation using the methods of natural science. Where there is a conflict between evidence available from the natural world and arguments based on philosophical reflection or pure reason, one needs to make a judgment about the relative strength of the evidence from the natural world and the philosophical reasoning. In this case, the natural science arguments against the existence of a literal Adam and Eve are compelling and the philosophical arguments you put forward in support of the idea are flawed.
**The natural science arguments are compelling. **
The existence of a literal Adam and Eve implies that all humans alive today descend from a single pair of parents who are the first representatives of a new species and who represent a sharp demarcation between humanity and other animals. The molecular and palaeontological evidence indicates otherwise. First, the number of ancient lineages at highly polymorphic loci arithmetically exceeds that which can pass through a bottleneck of two individuals; second, considerations from population genetics based on multiple studies using a range of methods on many different loci concur that the effective human population through Palaeolithic times is about 10,000 which is inconsistent with a bottleneck of two; third, the existence of a number of ancient haplotypes in nuclear genes is inconsistent with a simple single origin for modern humans and an extreme population bottleneck; fourth, the palaeontological evidence is that human powers of technology, language, symbolism, abstract thought and so on evolved gradually over more than a million years. Let’s look at each of these.
Various investigations of highly polymorphic loci in the primate genome, such as the Class II MHC genes, DRB1, DQB1 and DPB1 conclude that many more than four allelic lineages predate the divergence of humans and chimpanzees. Although recent work by Bergstrom et al have shown that amongst the 618 (!) known human alleles at DRB1 (Holdsworth et al, The HLA Dictionary 2008, Tissue Antigens 73, 95 – 170 (2009)) many rare alleles are of recent (ie in the last 500,000 years) origin, all studies have concluded that a substantial number of allelic lineages predate the divergence of humans and chimpanzees:
Ayala, The myth of Eve, Molecular biology and human origins, Science 270, 1930 – 1936
Ayala and Escalate, The evolution of human populations: a molecular perspective. Mol Phylogenet Evol 5,188–201.
Ayala et al, Molecular genetics of speciation and human origins, PNAS 91, 6787 – 6794 (1994)
Bergstrom et al, Recent Origin of DRB1 alleles and implications for human evolution, Nature Genetics 18, 237 (1998)
Bergstrom et al, Phylogenetic history of hominoid DRB1 loci and alleles inferred from intron sequences, Immunological reviews 167:351-365 (1999)
Klein J. & C. O’hUigin: Class II B Mhc motifs in an evolutionary perspective. Immunol Rev 143, 89-112 (1995)
Gongora et al, The HLA-DRB9 gene and the origin of HLA-DR haplotypes, *Human Immunology *51, 23 –31.
Svensson et al, Evolutionary relationship between human major histocompatibility complex HLA-DR haplotypes, Immunogenetics 43, 304 - 314
Since two individuals can carry, at most four different alleles at any given locus (and four different haplotypes of the class II region of the MHC), it is arithmetically impossible for the human lineage to have passed through a bottleneck of two (even if we ignore the fact that in a tiny population, one or more of those alleles might well drift to extinction). The Shiina paper that you cited against this is irrelevant to this conclusion (in fact it is irrelevant to the questions of human demography and phylogeny altogether) for reasons that I have already pointed out (primarily because the study is methodologically incapable of revealing any information about the phylogeny of the human DRB1 locus – I assume that you will read and absorb my more detailed explanation in my earlier post for why that is so and refrain from repeating the irrelevant quotation from the paper).
to be continued
**The natural science arguments are compelling. **
The existence of a literal Adam and Eve implies that all humans alive today descend from a single pair of parents who are the first representatives of a new species and who represent a sharp demarcation between humanity and other animals. The molecular and palaeontological evidence indicates otherwise. First, the number of ancient lineages at highly polymorphic loci arithmetically exceeds that which can pass through a bottleneck of two individuals; second, considerations from population genetics based on multiple studies using a range of methods on many different loci concur that the effective human population through Palaeolithic times is about 10,000 which is inconsistent with a bottleneck of two; third, the existence of a number of ancient haplotypes in nuclear genes is inconsistent with a simple single origin for modern humans and an extreme population bottleneck; fourth, the palaeontological evidence is that human powers of technology, language, symbolism, abstract thought and so on evolved gradually over more than a million years. Let’s look at each of these.
Various investigations of highly polymorphic loci in the primate genome, such as the Class II MHC genes, DRB1, DQB1 and DPB1 conclude that many more than four allelic lineages predate the divergence of humans and chimpanzees. Although recent work by Bergstrom et al have shown that amongst the 618 (!) known human alleles at DRB1 (Holdsworth et al, The HLA Dictionary 2008, Tissue Antigens 73, 95 – 170 (2009)) many rare alleles are of recent (ie in the last 500,000 years) origin, all studies have concluded that a substantial number of allelic lineages predate the divergence of humans and chimpanzees:
Ayala, The myth of Eve, Molecular biology and human origins, Science 270, 1930 – 1936
Ayala and Escalate, The evolution of human populations: a molecular perspective. Mol Phylogenet Evol 5,188–201.
Ayala et al, Molecular genetics of speciation and human origins, PNAS 91, 6787 – 6794 (1994)
Bergstrom et al, Recent Origin of DRB1 alleles and implications for human evolution, Nature Genetics 18, 237 (1998)
Bergstrom et al, Phylogenetic history of hominoid DRB1 loci and alleles inferred from intron sequences, Immunological reviews 167:351-365 (1999)
Klein J. & C. O’hUigin: Class II B Mhc motifs in an evolutionary perspective. Immunol Rev 143, 89-112 (1995)
Code:
In addition, other work shows that DR haplotypes (DR1 to DR16 of DRB1, and DR51 to DR53 of DRB3, DRB4 and DRB5) predate the divergence of human and chimp; for example:Svensson et al, Evolutionary relationship between human major histocompatibility complex HLA-DR haplotypes, Immunogenetics 43, 304 - 314
Since two individuals can carry, at most four different alleles at any given locus (and four different haplotypes of the class II region of the MHC), it is arithmetically impossible for the human lineage to have passed through a bottleneck of two (even if we ignore the fact that in a tiny population, one or more of those alleles might well drift to extinction). The Shiina paper that you cited against this is irrelevant to this conclusion (in fact it is irrelevant to the questions of human demography and phylogeny altogether) for reasons that I have already pointed out (primarily because the study is methodologically incapable of revealing any information about the phylogeny of the human DRB1 locus – I assume that you will read and absorb my more detailed explanation in my earlier post for why that is so and refrain from repeating the irrelevant quotation from the paper).
to be continued
H
hecd2
Guest
continuation
All that you are able to offer against my conclusion, other than the irrelevant Shiina citation, is a rather verbose and hand-waving argument about the tentativeness of scientific conclusions (and moreover one that confuses claims about the completeness of disciplines with errors in their findings – Newtonian mechanics itself was not “undercut”). Whilst any good scientist will agree that scientific conclusions are not formal proofs and are always formally subject to revision in the light of new evidence, this does not mean that we are unable to reach scientific conclusions in which we can have high confidence (otherwise, we’d never swallow a medicine, get on an aeroplane or cross the street). This is such a case. To be forceful, your objection would need more specifically to define a weakness in the argument that leads to the conclusion that the fact that humans and chimpanzees share more than four lineages at the DRB1 locus arithmetically precludes the possibility that humans have passed through a bottleneck of two individuals. It is not sufficient to say that some unspecified new finding might overturn our conclusion in some unspecified way, as this is a facile argument that can be used to dissent from any scientific conclusion at all, regardless of the quality of evidence in support of it. In truth, with this finding alone we are done, but let us look at the rest of the evidence that supports this conclusion.
You agree that there is overwhelming evidence that the effective human population in the Pleistocene (ie the period when modern humans emerged) was about 10,000, so we needn’t go into the extensive literature that reports analyses of multiple genetic markers (genes, pseudogenes, exons, introns, Alus, microsatellites, linkage disequilibrium etc) on autosomal, X, Y and mitochondrial chromosomes that all agree that the mean Ne was of the order of 10,000 with a minimum Ne of about 1,000 and no less than a few hundred at the minimum bottleneck. Amongst other effects, an extreme bottleneck would have left a substantial excess of recent rare alleles that we do not see. In order to show how a mean effective population of 10,000 can be compatible with a bottleneck of two, you point out, correctly, that the mean Ne over a number of generations is the harmonic mean of the effective population in each generation, and here I have substituted more precise figures for the ones you used) that if one starts with a population of two which then increases rapidly to 10,000 over the next ten generations and then remains at 10,000, Ne after 10,000 generations (200,000 years) is about 5,400. Leaving aside the fact that this number is less than even the smallest estimates of Ne, and predates the date of the main out-of-Africa event and the emergence of Homo sapiens sensu stricto by 100,000 years, the concept of a human population increasing from two to 10,000 in ten generations is not practically tenable. Of course, it is arithmetically possible, but it is trivial to propose an arithmetically possible population scenario that is not practically feasible. The question is not whether your scenario is arithmetically possible but whether it is practically feasible. There is no precedent for an increase in population by a factor of 2.5 generation on generation for ten generations, which is required in your scenario. In order to do so, every breeding couple would have to have a minimum of five children who survive to breeding age and who each have five children and so on. This ignores pre-maturation mortality (as high as 40% in a modern hunter-gatherer society: Hill et al, High adult mortality among Hiwi hunter-gatherers: Implications for human evolution, J Hum Evo 52, 443 - 454), and individuals who reach breeding age but who do not breed for any one of many reasons. All things considered, the fertility rate would have to be 10 for 10 generations (ie every breeding couple would have to be responsible for 10 live births). Although fertility rates as high as seven have been reported amongst hunter-gatherers, and as high as 10 amongst Hutterites (now declining), in neither case does the annual population growth rate (3% per annum amongst Ache and 4.1% amongst Hutterites) match that required by your scenario at 4.4% nor does it extend even half as long. Furthermore such high growth rates are totally unprecedented in a population growing from two individuals, with the degree of inbreeding that that entails and with the pressure on resources that would result in a 5000 fold increase in local population in 200 years (the population must remain sufficiently compact to breed approximately randomly if Ne is to increase proportionally with N).
to be continued
All that you are able to offer against my conclusion, other than the irrelevant Shiina citation, is a rather verbose and hand-waving argument about the tentativeness of scientific conclusions (and moreover one that confuses claims about the completeness of disciplines with errors in their findings – Newtonian mechanics itself was not “undercut”). Whilst any good scientist will agree that scientific conclusions are not formal proofs and are always formally subject to revision in the light of new evidence, this does not mean that we are unable to reach scientific conclusions in which we can have high confidence (otherwise, we’d never swallow a medicine, get on an aeroplane or cross the street). This is such a case. To be forceful, your objection would need more specifically to define a weakness in the argument that leads to the conclusion that the fact that humans and chimpanzees share more than four lineages at the DRB1 locus arithmetically precludes the possibility that humans have passed through a bottleneck of two individuals. It is not sufficient to say that some unspecified new finding might overturn our conclusion in some unspecified way, as this is a facile argument that can be used to dissent from any scientific conclusion at all, regardless of the quality of evidence in support of it. In truth, with this finding alone we are done, but let us look at the rest of the evidence that supports this conclusion.
You agree that there is overwhelming evidence that the effective human population in the Pleistocene (ie the period when modern humans emerged) was about 10,000, so we needn’t go into the extensive literature that reports analyses of multiple genetic markers (genes, pseudogenes, exons, introns, Alus, microsatellites, linkage disequilibrium etc) on autosomal, X, Y and mitochondrial chromosomes that all agree that the mean Ne was of the order of 10,000 with a minimum Ne of about 1,000 and no less than a few hundred at the minimum bottleneck. Amongst other effects, an extreme bottleneck would have left a substantial excess of recent rare alleles that we do not see. In order to show how a mean effective population of 10,000 can be compatible with a bottleneck of two, you point out, correctly, that the mean Ne over a number of generations is the harmonic mean of the effective population in each generation, and here I have substituted more precise figures for the ones you used) that if one starts with a population of two which then increases rapidly to 10,000 over the next ten generations and then remains at 10,000, Ne after 10,000 generations (200,000 years) is about 5,400. Leaving aside the fact that this number is less than even the smallest estimates of Ne, and predates the date of the main out-of-Africa event and the emergence of Homo sapiens sensu stricto by 100,000 years, the concept of a human population increasing from two to 10,000 in ten generations is not practically tenable. Of course, it is arithmetically possible, but it is trivial to propose an arithmetically possible population scenario that is not practically feasible. The question is not whether your scenario is arithmetically possible but whether it is practically feasible. There is no precedent for an increase in population by a factor of 2.5 generation on generation for ten generations, which is required in your scenario. In order to do so, every breeding couple would have to have a minimum of five children who survive to breeding age and who each have five children and so on. This ignores pre-maturation mortality (as high as 40% in a modern hunter-gatherer society: Hill et al, High adult mortality among Hiwi hunter-gatherers: Implications for human evolution, J Hum Evo 52, 443 - 454), and individuals who reach breeding age but who do not breed for any one of many reasons. All things considered, the fertility rate would have to be 10 for 10 generations (ie every breeding couple would have to be responsible for 10 live births). Although fertility rates as high as seven have been reported amongst hunter-gatherers, and as high as 10 amongst Hutterites (now declining), in neither case does the annual population growth rate (3% per annum amongst Ache and 4.1% amongst Hutterites) match that required by your scenario at 4.4% nor does it extend even half as long. Furthermore such high growth rates are totally unprecedented in a population growing from two individuals, with the degree of inbreeding that that entails and with the pressure on resources that would result in a 5000 fold increase in local population in 200 years (the population must remain sufficiently compact to breed approximately randomly if Ne is to increase proportionally with N).
to be continued
H
hecd2
Guest
continuation
It is a fact that ancient haplotypes cannot survive across severe bottlenecks, and especially such extreme bottlenecks as two individuals. This is even more the case for deleterious but recessive alleles. The coalescence of deleterious and neutral alleles are truncated at the bottleneck event. In other words, if there has been a bottleneck of two in the human lineage in the last several hundred thousand years, we would not expect to see ancient alleles or haplotypes in the human genome. But we do. Xiong et al, ‘No severe bottleneck during human evolution; evidence from two apolipoprotein C II alleles’, Am J Hum Genet 48, 383 –389 report two severely deleterious but recessive alleles at this locus that must have been derived from a common ancestral mutation more than 500,000 years ago. There are many others, including the X-chromosome non-coding locus Xp21.1 which has two haplotypes that diverged nearly 2 million years ago (Garrigan et al, Evidence for Archaic Asian ancestry on the human X chromosome, *Mol Biol Evol *22, 189 – 192 (2005)), and the pseudogene CMAHp on chromosome 6 which has haplotypes that diverged 2.9 million years ago (Hayakawa et al, Fixation of the human-specific CMP-N-acetylneuraminic acid hydroxylase pseudogene and implications of haplotype diversity for human evolution, Genetics 172, 1139 – 1146 (2005)). There are many others.
Furthermore, these and similar findings are resulting in refinements to the simple out-of-Africa model that so pleases you. Although the evidence overwhelmingly points to a recent migration out of Africa from a relatively small population (perhaps as small as 1000) which gives rise to the great part of the modern human genome in and out of Africa, there is increasing genetic evidence, such as that cited above, in support of multiple migrations which led to some breeding and genetic interchange of the migrants with the population descendant from earlier migrations, thus incorporating some genes into the Homo sapiens sapiens genome from archaic H sapiens or H erectus. See, for example, Templeton, Out of Africa again and again, Nature 416, 45 – 51. This is causing a refinement of the simple out-of-Africa model, which, while still excluding Wolpoff’s and others’ full-blown multi-regional scenario, yet results in a more complex ancestry for modern humans than is able to accommodate a sole ancestry of two in the last few hundred thousand years.
In your posts, you acknowledge the fact that the palaeontological evidence is that human faculties evolved slowly. In fact, the evidence for the domestic use of fire (a unique human capability) at Swartkans Member 3 and Zhoukoudian Locality 1 in the Lower Paleolithic, and the Oldowan tool culture, predate other evidence of human capability by hundreds of thousands of years. There is some evidence for use of pigments about 300,000 years ago, but no evidence of any purely aesthetic object (inscribed ochre) until 100,000 years ago in the Late Pleistocene. We have to wait until 35,000 years ago for the full flowering of Homo sapiens artistic ability in exquisite cave art and representational sculpture (the latter seems to be exclusively of an explicitly sexual nature, which must tell us something about our species). Similar gradual improvements are discernible in tool manufacture and technology, first immensely slow and then increasing exponentially in pace. Whilst Acheulean bifacials from 350,000 to 300,000 years BP are beautiful objects, they lack the sophistication and diversity of later tools and thus are congruent with the hypothesis of gradual acqusition of intellect. This is mirrored by the increasing encephalisation of hominins. McBrearty and Brooks, The Revolution that wasn’t: a new interpretation of the origin of modern human behaviour, J Hum Evol 39, 453 – 563 shows, amongst other things, that the idea that the bifacial is evidence for emergence of individuals that we would recognise as fully human is wrong, and that what we consider to be human behaviour does not appear other than in association with Homo sapiens sensu stricto at the earliest 200,000 years BP, and even then, gradually, over a period of some 150,000 years following. All of this compels the conclusion that our capacities developed gradually and that the idea that there was a profound change wrought in human cognition and intellect between one generation and the next at any stage of our evolution is profoundly contrary to the evidence. Your explanation that the faculties might have been there in potency but not in act is no more than special pleading to rescue a failed hypothesis. It’s not just that evidence is lacking for a sudden emergence of human capacities, but that the evidence that we do have, contradicts it.
to be continued
It is a fact that ancient haplotypes cannot survive across severe bottlenecks, and especially such extreme bottlenecks as two individuals. This is even more the case for deleterious but recessive alleles. The coalescence of deleterious and neutral alleles are truncated at the bottleneck event. In other words, if there has been a bottleneck of two in the human lineage in the last several hundred thousand years, we would not expect to see ancient alleles or haplotypes in the human genome. But we do. Xiong et al, ‘No severe bottleneck during human evolution; evidence from two apolipoprotein C II alleles’, Am J Hum Genet 48, 383 –389 report two severely deleterious but recessive alleles at this locus that must have been derived from a common ancestral mutation more than 500,000 years ago. There are many others, including the X-chromosome non-coding locus Xp21.1 which has two haplotypes that diverged nearly 2 million years ago (Garrigan et al, Evidence for Archaic Asian ancestry on the human X chromosome, *Mol Biol Evol *22, 189 – 192 (2005)), and the pseudogene CMAHp on chromosome 6 which has haplotypes that diverged 2.9 million years ago (Hayakawa et al, Fixation of the human-specific CMP-N-acetylneuraminic acid hydroxylase pseudogene and implications of haplotype diversity for human evolution, Genetics 172, 1139 – 1146 (2005)). There are many others.
Furthermore, these and similar findings are resulting in refinements to the simple out-of-Africa model that so pleases you. Although the evidence overwhelmingly points to a recent migration out of Africa from a relatively small population (perhaps as small as 1000) which gives rise to the great part of the modern human genome in and out of Africa, there is increasing genetic evidence, such as that cited above, in support of multiple migrations which led to some breeding and genetic interchange of the migrants with the population descendant from earlier migrations, thus incorporating some genes into the Homo sapiens sapiens genome from archaic H sapiens or H erectus. See, for example, Templeton, Out of Africa again and again, Nature 416, 45 – 51. This is causing a refinement of the simple out-of-Africa model, which, while still excluding Wolpoff’s and others’ full-blown multi-regional scenario, yet results in a more complex ancestry for modern humans than is able to accommodate a sole ancestry of two in the last few hundred thousand years.
In your posts, you acknowledge the fact that the palaeontological evidence is that human faculties evolved slowly. In fact, the evidence for the domestic use of fire (a unique human capability) at Swartkans Member 3 and Zhoukoudian Locality 1 in the Lower Paleolithic, and the Oldowan tool culture, predate other evidence of human capability by hundreds of thousands of years. There is some evidence for use of pigments about 300,000 years ago, but no evidence of any purely aesthetic object (inscribed ochre) until 100,000 years ago in the Late Pleistocene. We have to wait until 35,000 years ago for the full flowering of Homo sapiens artistic ability in exquisite cave art and representational sculpture (the latter seems to be exclusively of an explicitly sexual nature, which must tell us something about our species). Similar gradual improvements are discernible in tool manufacture and technology, first immensely slow and then increasing exponentially in pace. Whilst Acheulean bifacials from 350,000 to 300,000 years BP are beautiful objects, they lack the sophistication and diversity of later tools and thus are congruent with the hypothesis of gradual acqusition of intellect. This is mirrored by the increasing encephalisation of hominins. McBrearty and Brooks, The Revolution that wasn’t: a new interpretation of the origin of modern human behaviour, J Hum Evol 39, 453 – 563 shows, amongst other things, that the idea that the bifacial is evidence for emergence of individuals that we would recognise as fully human is wrong, and that what we consider to be human behaviour does not appear other than in association with Homo sapiens sensu stricto at the earliest 200,000 years BP, and even then, gradually, over a period of some 150,000 years following. All of this compels the conclusion that our capacities developed gradually and that the idea that there was a profound change wrought in human cognition and intellect between one generation and the next at any stage of our evolution is profoundly contrary to the evidence. Your explanation that the faculties might have been there in potency but not in act is no more than special pleading to rescue a failed hypothesis. It’s not just that evidence is lacking for a sudden emergence of human capacities, but that the evidence that we do have, contradicts it.
to be continued
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