Tag Archives: Human Evolution

Nyamulagira Volcano and Human Evolution

I had mentioned earlier that the volcanoes of the Virugna region in the Western Rift Valley (as well as other highland spots) have often been islands of rain forest separated from each other by different habitats, including grasslands and wooded savannas. this has produced an island effect that has been a laboratory for evolution, and it is likely that these forest islands (and others in the greater region of east Central Africa and western East Africa) have been the loci of evolution of many endemic species. (See Island Africa: The Evolution of Africa’s Rare Animals and Plants by Kingdon for an excellent overview of the Island Effect in highland regions of Central and East Africa.)

It is probably not a coincidence that two of the three subspecies of gorilla live within sight of each other (and of the main subspecies, the lowland gorilla) within this region. The Virunga volcanoes are not old enough to have supported island forests for the evolution of these specific subspecies, but other highlands in the region, or other volcanoes (perhaps in the Eastern Rift) may well have been the location in which they evolved.

And, as it turns out, there is reason to believe that the split between chimps and humans occurred on one of these volcanic mountain tops several million years ago. Or, at least, in an environment geologically similar to the upper reaches of the Virunga Volcanoes. But to tell this story right, I have to go back a few years.
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Richard Dawkins defends theory of evolution

He talks about his book, The Greatest Show on Earth: The Evidence for Evolution. The interviewer is not my favorite interviewer. A public radio interviewer should not even be asking questions about religion and creationism unless doing a story that is explicitly on fringe beliefs. She digs in just after 16 minutes with the meany atheist thing. But here you have it:

Is the latest claim regarding “chimp-human” inbreeding a bunch of hooey?

Yes, but not necessarily because it is wrong.

ResearchBlogging.orgSome time ago researchers proposed that the modern DNA signal indicated that chimps and humans continued to interbreed long after they split in evolutionary time. A new study refutes this, and as the author states, this new study is more correct because it “simpler and hence more likely”.

Wow.
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Is it a Falsehood that Humans Evolve from Apes?

This is another falsehood, but a tricky one. Remember the point of falsehoods: They are statements that are typically associated with meanings or implications that are misleading or incorrect, and in some cases downright damaging. “Humans evolved from apes” is an excellent example of a falsehood because it is technically correct, yet the implied meanings that arise from it are potentially wrong. Even more importantly, you can’t really analyze the statement “Humans evolved from apes” without getting into an extended analysis and discussion of what an ape is and what a human is.
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Size and Scaling in Hominid Evolution

ResearchBlogging.orgStephen Jay Gould and David Pilbeam wrote a paper in 1974 that was shown ten years later to be so totally wrong in its conclusions that it has fallen into an obscurity not usually linked to either Gould or Pilbeam. However, they were actually right in ways that they could not have anticipated. And even if they were not right, this paper still has much to contribute, including the opening words of that publication in Science, which are very much worthy of consideration for many reasons:

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Two chimps walked into a bar …

… and made a real mess of the place when one of them spotted the jar of pickles on the counter. They fought over it until one of them had almost all the pickles and the other one had a number of bruises and a tiny fragment of one pickle that the other chimp dropped by accident.

That would be the way it would happen if two chimps walked into a bar. Or imagine two chimps, and each finds a nice juicy bit of fruit out in the forest. And instead of eating the fruit, because they are not hungry, they carry it around for a while (this would never happen, but pretend) and then accidentally run into each other. What would happen? Same thing. Event though neither chimp actually needed the fruit and each chimp had its own fruit, the dominant chimp (between the two) would end up with both pieces of fruit.

This is why chimps could not possibly cooperate in any effort to scour the forest for various edible items, bring them all back to a central place, share and then cooperatively process the food items, and ultimately produce a meal that is eaten by all of the chimps on an as needed basis. Humans do that but chimps can’t. Explain this and you explain one of the major features of human evolution…
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Great Moments in Human Evolution: The Invention of Chipped Stone Tools

Or not.

Much is made of the early use of stone tools by human ancestors. Darwin saw the freeing of the hands ad co-evolving with the use of the hands to make and use tools which co-evolved with the big brain. And that would make the initial appearance of stone tools in the archaeological record a great and momentous thing. However, things did not work out that way.
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How diverse were early hominoids?

And hominids.

We know the fossil record underestimates diversity at least a little, and we know that forested environments in Africa tend to be underrepresented. Given this, the diversity of Miocene apes may have been rather impressive, because there is a fairly high diversity in what we can assume is a biased record.

But I’d like to make the argument from another angle, that of modern ecological analogues. Let us assume that the greater apparent diversity of apes in the middle and late Miocene compared today can be accurately translated as a modern reduction in ape diversity. Not counting the relatively diverse lesser apes, there are five species (2 chimps, gorilla, human, orang) which can be further divided into 10 subspecies, across the entire old world.

Now look at the size range of all of the living apes. Gibbons are the smallest and gorillas the largest. When a family or subfamily of land mammal is diverse in a particular region (a biome or something larger than a biome) we tend to see that diversity played out along a spectrum of size, and against size we can find additional diversity derived from dietary or subhabitat differences and geography. It seems to me that there is room in the size spectrum between gibbons and chimps, and orangs and gorillas, and there is certainly room above the gorilla size as indicated by the existence in the fossil record of very large Asian forms.

We know that some of the later Miocene apes were bipedal, and it is starting to look like bipedalism or something like bipedalism is showing up among other apes in the Miocene as well. So perhaps there is a spectrum of locomotory pattern along which diversity may be spread.

This gives us a the following size classes: gibbon, siamang, [something in between], chimp, orang, [something in between], goriilla, [something bigger], or at total (a minimum?) of eight size classes across which apes might exist in a world in which apes are divers. Like the Miocene. If we add to this a more arboral form and a more bipedal form, perhaps we double the number, or perhaps we add about five new classes (I’m guessing that a Mighty Joe Young size ape would not have been bipedal!). This gives us about a dozen, conservatively estimated, niches when we divvy up size and so-called positional behavior.

To this we can add geography. It is probably reasonable to assume that a wetter, more forested middle and late Miocene Africa could be divided into at least four or regions, between the West/Central divide that modern biogeogrpahy tells us was effective at least in the Late Miocene, the Congo River divide, North/Central Africa, East Africa and Southern Africa. Let’s conservatively assume four, and let’s assume that only half (six) of the hypothesized ape species are divided among these areas. That means that 24 species are endemic to varoius regions, and six additional species are more widely spread for a conservative estimate of 30 species.

Among these species there may have been several bipedal forms, but only one of them (plus or minus a little hybridization hanky panky here and there) would have been the human ancestor. Of course, no one at the time suspected that …. (Or they probably would have done something about it.)

This is not an outrageous suggestion. The idea that if you went back in time to a more ape-rich time (and we know it was more ape-rich) and got a current copy of the Guide to the Mammals of Africa, the ape section would have a few dozen species, just like the monkey section or the antelope section today has a few dozen species.

Go apes!

Neanderthal Genome Will Be Released

The complete genome of a Neanderthal dating to about 38,000 years ago has been sequenced by the team lead by Svante Paabo. The genome will be announced on Darwin’s Birthay, Feb 12.

“We are working like crazy at the moment,” says Pääbo, adding that his Max Planck colleague, computational biologist Richard Green, is coordinating the analysis of the genome’s 3 billion base pairs.

Comparisons with the human genome may uncover evidence of interbreeding between Neanderthals and humans, the genomes of which overlap by more than 99%. They certainly had enough time for fraternization — Homo sapiens emerged as a separate species by about 400,000 years ago, and Neanderthals became extinct just 30,000 years ago. Their last common ancestor lived about 660,000 years ago, give or take 140,000 years.

Nature

Despite the remarks made in the Nature coverage about interbreeding, Svante has indicated in previous discussions about this genome that there is nothing to indicate this in the present analysis.