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thistle
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I don’t understand. You, me, the other posters have the same brain size. What living humans have smaller brains than us?
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abcdefg
Guest
each human’s brain size is different! do a search and see.
adults brain weight ranges from 1,300g to 1,400g
faculty.washington.edu/chudler/brainsize.html
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abcdefg
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The normal adult human brain typically weighs between 1 and 1.5 kg (three pounds) en.wikipedia.org/wiki/Human_brain
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thistle
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That’s being pedantic. I know our brains are not EXACTLY the same size. When we talk about same size brains 1300g to 1400g is considered basically the same. You can’t possibly mean someone with a 1300g brain is genetically inferior to someone with a 1400g brain, do you?
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abcdefg
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If you consider apes are human’s ancestor. a brain of 1300g is far superior than an monkey’s 97g.
You’re confusing me by arguing on my side.
You should realize if a slightly larger brain has no advantage then natural selection can’t work on human/ape at all. the biggest advantage humans have over (other) apes is the brain.
each mutation can only generate a slight change in brain size (smaller than 1/14 I would imagine, obvious but datas are welcome). it’s simiply impossible a single mutation can turn a 97g brain into a 1300g one.
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Milliardo
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That’s right: one such condition that does not permit apes to evolve further yet is because of the dominance of homo sapien; in other words, there’s no motivation for them to evolve any further since we, directly or indirectly, hamper their development. To give a little bit more of an example here, when dinosaurs ruled the Earth, mammals were rather small. That’s because the dinosaurs dominated them in every aspect. Only after the dinosaurs ceased to exist did mammals began to slowly dominate. The same then can be said about other animals, especially the apes.
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abcdefg
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According to ET, whether something can evolute or not has nothing to do with its will. mutations happen whether he likes it or not. the the result is purged by nature. the notion that one evolutes only when one has the motivation/desire to evolute is called Lamarckism(see zian’s post).
also according to ET, nothing can hamper an evolution process without hampering mutations. the domination of dinosours doesn’t delay the appearence more complex life forms(human for example). human activities like polution, radioactivity experiments actually make mutations easier. Humans also don’t intentionally kill smart apes.
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Milliardo
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I am not sure about that; after all, we have to factor in the environment as well, the conditions which led to its evolution, etc. It didn’t just happen without any cause or reason.[/fnt]
Based on what I’ve learned about evolution, this seems to be not the case. Again, case-in-point would be the mammals being hardly noticed during the age of dinosaurs; they flourished only after the dinosaurs ceased to exist.
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rossum
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Only part of the story, better to say “through mutation and natural selection”. You left out “natural selection”, which is very important.
Better to say species rather than tribe.
This is basically correct. Ten million years ago there were a lot more forests in Africa than there are now. There were various species of tree-living apes in that forest. Around five million years ago the climate began to dry out and the forests began to shrink. This resulted in areas of more open tree-savanah. This was a new environment and some of the apes, our ancestors, moved into the new environment and began to exploit it. Other apes remained in the forests and continued much as before. At this stage our ancestors walked upright, but still had brains roughly the size of a chipanzee.
This is the wrong way round. Tool use did not drive the increase in brain power. Increased tool use was a result of the increase in brain power. The increase in brain power was probably driven by the climate and predation. In a tree-savannah there is a reasonably simple strategy for avoiding large predators like lions - run to the nearest tree and climb it. Unfortunately the climate was continuting to dry out and the trees were getting further and further apart. The simple strategy no longer worked as well since the tree was further away and the lion was more likely to catch you before you reached it. Only those of our ancestors who could outthink a lion survived to reproduce. In an open savannah brains were a definite help to survival.
The accounts do not conflict. You left out natural selection which is the link between the external environment (“History books”) and the internal changes to DNA (“Biology books”). When the lions ate those hominids that couldn’t outthink them, they also ate their DNA. Every one of your ancestors succeeded in outthinking the lions and reproducing before they died, thus making sure that their DNA survived. You and I are both descended from a very very long line of billions of successful reproducers stretching all the way back to the first proto-cell some 3.7 billion years ago. If an organism failed to reproduce then that organism has no living descendants. Any ancestor with a genetic advantage would pass on that advantage to its descendants in their DNA. The gradual accumulation of small advantages leads to a large advantage, such as a very large brain, coded into DNA.
Big brains are costly, they take energy to build and energy to run. If a big brain is not needed then it is a disadvantage, not an advantage. For a forest living ape the old strategy of “run to the nearest tree and climb it” still works very well. The have no need for a larger brain than they already have. Should a group of apes come out of the forest and try living in the open land then, unlike our ancestors, they would find an upright-walking large-brained primate already established. It is very difficult to replace an established species in a new-to-you ecological niche since the established species is usually better adapted to that niche than you are.
That is the reason why the extinction of the dinosaurs was so important. When the K-T meteorite impact wiped out the dinosaurs there were a lot of land dwelling ecological niches left empty for the mammals to expand into. Flying dinosaurs (birds) survived so mammals were much less successful at filling airborne niches since those were already filled.
In short, yes in principle modern apes could evolve a brain as big as a human. They don’t because that particular ecological niche is already filled.
rossum
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abcdefg
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But I’m sure about it. you can ask those die-hard evolutionists if they’re sure about it.
However give you 2 examples here. Cancer is due to bad mutation. no one wants that kind of mutation, yet it still happens.
the other is in the 1st post about wings
According to ET, since mammals are more complex, they’ll appear later. it’s not because of the domination of dinosaurs that there’s no large mammals. it’s become the time hasn’t come for large mammals to appear.
you seems to suggest the domination of a kind of animal delay the appearence of more complex species. let me ask you there’re domination of bacterias, insects, fish, reptiles. according to ET all these helped or hampered the appearence mammals?
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abcdefg
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natural selection only extincts species and doesn’t encourage mutations one bit. eugenism is human’s attempt to practise a faster form of “natural selection”
They’re not different species at the beginning of separation. living on the trees or ground, they’re still ancient apes until DNA mutations occured.
I previously plan to reply to previous passages but after reading this passage I decide there’s no such necessity. mutations happens on an atom and cells level. atoms and cells could never know if a ecological niche is filled. atoms and cells also don’t know what their owners’ thoughts are. they just react to chemicals and radio-waves (UV, gamma ray) that can reach them.
for individual apes now living deep in the forests they never know there’re humans dominating the outside world, yet they still don’t develop
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cheddarsox
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Intelligence is not the only factor in success. Many animals with very limited intelligence, or none by human standards, are extremely successful. Intelligence is only useful if one has the means of putting it to work. Often instinct is as good or better at keeping a critter alive and breeding.
Radioactivity is not the only thing that encourages more mutations. Mutations happen ALL the time, and yes enviornmental changes, ie, new food sources, different minerals available etc, can certainly affect DNA . Sometimes genes are turned on and off by certain factors, and mutations that have already taken place but havent’ made much difference suddenly matter a whole lot due to changes in the enviornment or diet.
The information is available, if you care to look for it.
The complexity and awesomeness always make me more aware and humble before the divine, not less. “Your ways are not our ways…” No human could have thought this up.
cheddar
Radioactivity is not the only thing that encourages more mutations. Mutations happen ALL the time, and yes enviornmental changes, ie, new food sources, different minerals available etc, can certainly affect DNA . Sometimes genes are turned on and off by certain factors, and mutations that have already taken place but havent’ made much difference suddenly matter a whole lot due to changes in the enviornment or diet.
The information is available, if you care to look for it.
The complexity and awesomeness always make me more aware and humble before the divine, not less. “Your ways are not our ways…” No human could have thought this up.
cheddar
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abcdefg
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But we are comparing humans and apes in this topic. only in intelligence human have a clear advantage.
Don’t go off-topic
Mutations that can affect the identity of an individual don’t.
if you move to Africa from Europe, your skin become darker. you can call this a mutation, however it doesn’t affect your DNA, and while your skin can’t be any darker, you’re unlikely to bear a child even has the slightest color. while I don’t know how eating Chinese food instead of Western food affects one’s health, one thing is certain, criminals can’t get away from police DNA identification by doing this.
This belong to that theology thread.
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abcdefg
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But we are comparing humans and apes in this topic. only in intelligence human have a clear advantage.
Don’t go off-topic
Mutations that can change the DNA of an individual don’t happen easily (good or bad).
if you move to Africa from Europe, your skin become darker. you can call this a mutation, however it doesn’t affect your DNA, and while your skin can’t be any darker, you’re unlikely to bear a child even has the slightest color. while I don’t know how eating Chinese food instead of Western food affects one’s health, one thing is certain, criminals can’t get away from police DNA identification by doing this.
Scientists prefer taking plants to space in the hope of a good mutation caused by space rays(?). they don’t feed plants different fertilizers to encourage DNA mutations.
This belongs to that theology thread. forums.catholic-questions.org/showthread.php?t=91535
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PLP
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You seem to be under the misapprehension that a new feature in a species, such as a big brain, happens because of a single mutation. This is not the case. The central tenet of scientific Evolution is that new features arise by accumulating many variations (of which mutation is only one type of variation), each of which confers a small selective advantage.
The mutations and variations are also often indirect. In humans, our big brains are the result not of variations that just make the brains bigger, but rather of variations that greatly extend the natal and juvenile body development plan; since primate neonates and juveniles have a higher brain to body ratio, extending this development plan has the effect of creating bigger brains.
No other species differentiated from our cousins after we did because (as mentioned earlier) we ourselves already filled the ecological niche best filled by walking-upright-big-brained organisms. Any later, small variation which would make this niche available would be selected against because the niche was already filled by our own ancestors.
The mutations and variations are also often indirect. In humans, our big brains are the result not of variations that just make the brains bigger, but rather of variations that greatly extend the natal and juvenile body development plan; since primate neonates and juveniles have a higher brain to body ratio, extending this development plan has the effect of creating bigger brains.
No other species differentiated from our cousins after we did because (as mentioned earlier) we ourselves already filled the ecological niche best filled by walking-upright-big-brained organisms. Any later, small variation which would make this niche available would be selected against because the niche was already filled by our own ancestors.
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EnterTheBowser
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The environment, as you’ve said, does little to encourage certain kinds of mutations. Those happen randomly. But the environment does (afterwards) select for various non-random sorts of mutations.
In other words, let’s look at the bit about ecological niches. Mutations that make chimps more suited towards filling our niche happen all the time. But they’re not selected for because we fill that niche pretty thoroughly.
Nobody meant to say that natural selection causes the individual cells to mutate in the way that’s being “selected for.” Rather, natural selection filters all the random mutations that occur in cells.
In other words, let’s look at the bit about ecological niches. Mutations that make chimps more suited towards filling our niche happen all the time. But they’re not selected for because we fill that niche pretty thoroughly.
Nobody meant to say that natural selection causes the individual cells to mutate in the way that’s being “selected for.” Rather, natural selection filters all the random mutations that occur in cells.
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zian
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Eugenics is not “natural selection”. it is intelligent (Not!
) design. 
I take it you mean “molecular”, not atomic.
Many species are threatened, through poaching and loss of habitat; I think they “know” something is different.
“Yet they still don’t develop”? You seem to be laboring under the misconception that evolution suggests that species must develop or progress. This is incorrect. There is no “forward arrow of progress” or development in evolution.
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zian
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False. Also, opposable thumb, articulation of bones in the arm and shoulder and neck, upright gait, language facilities that promote improved social communication and interaction, muscular and bone structure of the foot, etc., ; the list goes on. Then again, in the forest canopy environment, the local apes are the superior species, because they are adapted to it.
Really? Why? I suppose if I get a tan …
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steveandersen
Guest
Sigh, I’m not going to respect myself in the morning but…
abcdefg:
(1) Monkeys aren’t hominids
(2) the process doesn’t necessarily need mutation. Natural variance and isolated populations work just as well
abcdefg:
But of course not the only way
abcdefg:
abcdefg:
abcdefg:
abcdefg:
Are you suggesting that there must be some radiation damage for evolution to take place?
You’re joking right?
abcdefg:
Evolution can work just as well by not purging some traits and thus making them more common.
Remember evolution is not about making something “better” just different.
abcdefg:
First of all they would have to become bipedal or otherwise change the size of the birth canal to support larger brains. That is where we really began to differ.
abcdefg:
What do you think evolution is some sort of cheap Sci-Fi movie effect?
abcdefg:
Evolution only states that isolated populations will diverge. This divergence can be due to many things from natural selective pressures, to mutations, to plain old genetic drift.
I would think that due to human encroachment the isolation of ape populations is greatly increased so it is possible that there is more evolution occurring in those populations now than previously.
That’s not quite right
(1) Monkeys aren’t hominids
(2) the process doesn’t necessarily need mutation. Natural variance and isolated populations work just as well
I’m not sure I’d phrase it that way but in general terms, yes climate change is a big way to isolate populations and to put them under selective stress.
But of course not the only way
Why?
Why?
As some have already pointed out the idea of passing on acquired traits is an old discredited theory that was superceded by evolution
I’m not sure what you are saying here.
Are you suggesting that there must be some radiation damage for evolution to take place?
You’re joking right?
Once again not quite right
Evolution can work just as well by not purging some traits and thus making them more common.
Remember evolution is not about making something “better” just different.
Well I suppose they could, given the right conditions
First of all they would have to become bipedal or otherwise change the size of the birth canal to support larger brains. That is where we really began to differ.
What is this preoccupation with radiation and damaged cells
What do you think evolution is some sort of cheap Sci-Fi movie effect?
Explain what?
Evolution only states that isolated populations will diverge. This divergence can be due to many things from natural selective pressures, to mutations, to plain old genetic drift.
I would think that due to human encroachment the isolation of ape populations is greatly increased so it is possible that there is more evolution occurring in those populations now than previously.
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rossum
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abcdefg (post #31):
abcdefg:
abcdefg:
abcdefg (post #33):
rossum
You are correct to say that natural selection has no effect on either the rate or type of mutations that happen. The effects of natural selection cover a lot more that the extinction of species. Bacteria have evolved resistance to many antibiotics; this was due to the action of natural selection. Any mutation that helped a bacterium to survive in the presence of the antibiotic would tend to help that bacterium reproduce and to spread that mutation through more of the population. The end result of this process is a population of bacteria that are immune to that antibiotic.
Correct, mutations are random with respect to their effect on the phenotype. There is nothing to make the mutations tend to prefer one type of ecological niche to another.
Forest dwelling apes could well have mutations that would make them slightly better suited for life in open land, for instance a minor modification of their hip joint to make it a little easier to walk upright. The problem is that as soon as they tried to make use of their minor improvement, they would come into contact with humans who have a hip joint much better adapted to upright walking. For those apes there would be no advantage to the improved hip because they would not be able to use it to expand into new territory. If there is no advantage to the mutation then it will not be favoured by natural selection. Such mutations might be happening all the time, it is just that at the moment they do not confer any advantage so they are not favoured by natural selection.
abcdefg (post #33):
Mutations in DNA happen a lot more easily than you seem to think. The average human has about 100 mutations in their DNA. The majority of these are neutral having no effect on the individual. About five will have some sort of effect, mostly very slight. Those with an effect will be mostly bad with the occasional good one. Good or bad will always be dependent on the environment; a mutation that is good in one environment might be bad in a different environment.
rossum
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