Perhaps so, but maybe instead of simply attributing total ignorance to me, you might tell us what the most important conclusions are concerning ar ramidus and why we should think them.
Perhaps you should just read the work.
“In modern monkeys and apes, the upper canine is important in male agonistic behavior, so its subdued shape in early hominids and Ar. ramidus suggests that sexual selection played a primary role in canine reduction.”
Now, to me, that’s a leap. How do they know this, and why are they persuaded of it? Did they interview Ar ramidus women and find that 9 out of 10 thought large upper canines unattractive? Obviously, they didn’t. Human weapons, even early on, were more dangerous, and got progressively more so as time went on. Why was that weapon-making trait successful and progressive in humans while apes pretty much just got stuck with big muscles and big canines? And why do female apes not recoil from their large-toothed males in favor of those with smaller teeth, if female Ar ramidus thought it sensible to do so?
The answers to many of these questions are to be found in Suwa et al, Paleobiological Implications of the
Ardipithecus ramidus Dentition, Science 326, 94 - 99 and in the papers cited in that one. The conclusions of progressive reduction in upper canine size, change in canine morphology, the loss of honing in the CP3 complex which begin with Miocene apes and continue through
Orrorin tungenensis, Sahelanthropus tchandensis, Ar kadabba, the australopithecenes and Homo to modern humans is robustly evidenced. Combining that with observations about timing of canine eruption in
Ar ramidus, extant apes and extant humans, and simultaneous reductions in sexual dimorphism and observations that an enhanced UC is critical to sexual success in
Pan troglodytes and other primates, leads to the reasonable hypothesis that a large UC and honing in CP3 complex (along with sexual dimorphism) are conserved in conditions of physical male-male sexual competition and have been lost in the human lineage by relaxed selection.
Sexual selection does not just mean mate selection as you seem to think, but also (in fact primarily) includes traits deriving from male-male sex-related conflict, as in this case.
Oh, and did you miss the point that
Ar ramidus pre-dates tool use by 2.5 million years?
Are the “racial” variations in teeth (Australoids perhaps being the most interesting) of modern men due to sexual selection as well? Or is that something else entirely, and not particularly important from an evolutionary standpoint? If not important, then why do those differences exist? What differences should we consider important and why?
Well there are natural variations within any species in any parameter that you care to measure, and some can be shown to be selected for (for example skin pigmentation) and others represent no more than random drift. But differences become important from an evolutionary point of view when they fall outside the intraspecific range. In the case of the male UC, modern human crown height ranges from 7 to 10mm,
Ar ramidus from 9 to 12mm, in chimpanzee from 13mm to 19mm and in gorilla from 18 to 26mm. Even more significantly the difference between male and female in humans is 4% to 9%, in
Ar ramidus from 10% to 15% and in modern great apes from 19% to 47%.
But to me, the “food carrying” explanation for ancient ancestors’ walking upright is just not adequate for many reasons; not the least of them being that many animals that don’t even have hands carry food, and some of them do it a lot better than we do.
Well, I don’t think this hypothesis is as simplistic as you represent it if you read the work, but in any case you need to look at the food carrying capabilities of apes, not just any animal.
And how many ar ramidus have they actually found? Isn’t it just one?
No, specimens representing about 35 individuals from Aramis, with a minimum of 14 individuals for both upper canine and upper second molar, plus seven individuals from another site.
If I recall correctly, when I first heard about it, they weren’t even sure whether the partial skeleton was that of a male or a female.
A probable female because of the relative size of UC and post-cranium.
What I was attempting to convey is that the bases for many of the conclusions people derive from things like a single partial skeleton or a mashed lemur are wonderously thin.
What you have shown is that your knowledge of the evidence and conclusions presented in the suite of research papers is wondrously thin. I recommend that you read the actual work before you leap in to criticise it.
Alec
evolutionpages.com
).
