Quoting Bloggingheads: After the recording of this diavlog, Razib wrote in with the following correction:

i made a verbal flub at the end of the diavlog which i think will confuse viewers & listeners A LOT (though i think john corrected for the flub in his mind since he knows the territory).

i said: "most lineages outside of eurasia are derived from india."

i meant to say: "most lineages outside of african are derived from india."

If anyone is interested, just for the record, that moment is here. Thanks for sending in the correction, Razib. And thanks also for a truly wonderful diavlog. Your questions, along with John's rare gift for making clear how science is done in the real world, set a high standard for Science Saturday and indeed, for scientific outreach to the interested lay audience overall.

On the way populations spread across the surface of the earth, has anyone tried a kind of gas diffusion model? I mean in two dimensions with valleys, mountain passes, ocean barriers, etc., looking not for actual history, which would undoubtedly play out differently on each successive run, but rather looking for general patterns in terms of back flows, inter-mixtures, and so on? This might especially apply during the period between out-of-Africa and the end of the Paleolithic, when technology was relatively uniform and no population had an obvious advantage. Or would differential selection for traits in tropical vs. temperate climate areas mess it all up? Just a thought from an old man in a dry season.

You may look into this link: http://channel.nationalgeographic.co...06-interactive The gene migration is well documented, the geographic issues of sea levels, ground passages are a different story...

Damn. Hawks is good. Would love to hear his views on Aaron Filler's "Upright Ape". A suggestion for a future diavlog would be a wide-ranging Hawks/Frans De Waal discussion on primate evolution, behavior, etc.

The whole diavlog was a great idea, since by sheer chance their last conversation was posted a day or so before the Biggest Bang of the last several decades in the field. This was a good fleshing out of what we know so far and what it means about Ardi. It was also interesting to learn how this multidisciplinary team kept a lid on what they were doing and suddenly published 30 simultaneous papers. Maybe it's a good thing scientists aren't running the government; we'd never get any good leaks. One question: Where was the Timneh?

the parrot pipes up near the end of the discussion fwiw.

..the parrot pipes up near the end of the discussion fwiw.

Nice! His or her sexually non-dimorphous self makes my day Bheads day. We've previously had a few BH dogs, cats and homo sapiens babies, but yours is the first psitticine for sure. Gratuitous and off-topic fundraising pitch: Save parrots here!

This was very interesting, especially the section about the origins of different populations and the differences within those populations.
More studies of more populations please.

Such a pleasure to listen to Hawks. He gives much needed balance to many of the (speculative) claims that are being made about the Ardi findings and gives very reasoned explanations about and context for what can and can't be concluded from those findings. More of the science that gets into the public sphere should be of that variety. What was rather confusing initially was that Razib and John seemed to be basing their comments in the beginning of the diavlog on the assumption that the last human/chimp common ancestor lived more recently than Ardi (~4.3 mya versus ~4.4 mya). This seems to come from here, in John's SEED magazine article: "So how close is Ardipithecus to the last common ancestor? In the current issue of Genetics, yet another study of the human and chimpanzee genomes places the divergence between them at only 4.3 million years—a shade younger than Ardipithecus. So far it is not clear how accurate such estimates are, but ever since a draft chimpanzee genome became available earlier this decade, estimates have not placed the common ancestor much older." However, Lovejoy's article, prior genetic research, and most

However, Lovejoy's article, prior genetic research, and most popular science information refer to the the assumption that the last human/chimp common ancestor lived 5-6 mya. It would have been helpful for John and Razib to have clarified this dating distinction at the beginning of the diavlog, so that the context of some of their comments could have been more readily understood.

Good point. This is a real question right now; nearly all recent genetic studies put the date of population divergence around 4 million years ago, but if you dig up an early fossil, you clearly would rather have a higher date. A higher date may well be possible, as the genetic comparisons do involve some assumptions that might be in error. I think the Ardi papers have done an interesting thing -- basically argued that most of the features that *might* show it on the human lineage are actually ancestral retentions from Miocene apes. But if so, that enhances the probability that it *is* one of those apes, possibly the human-chimpanzee ancestral population, possibly not. --John

john corrected for the flub in his mind

That gives me a lot more credit than I deserve...

But if so, that enhances the probability that it *is* one of those apes, possibly the human-chimpanzee ancestral population, possibly not.

John, If, given current knowledge, you had to put a probability number on this being the case, how high would you go?

Quoting Wonderment: John, If, given current knowledge, you had to put a probability number on this being the case, how high would you go?

Ardipithecus is very much the borderline case. White and team have Ardipithecus kadabba at 5.5 million and Ardipithecus ramidus at 4.4. I'd put the probability of Ar. kadabba being a non-hominin at 75 percent; with Ar. ramidus I'm more easily persuaded that it may be a hominin and still be consistent with the genetics. But it's hard to find much anatomy to argue in that direction; it's really only the small canines and the *possibility* that the pelvis reflects better upright stance.

But it's hard to find much anatomy to argue in that direction; it's really only the small canines and the *possibility* that the pelvis reflects better upright stance.

Oh, and the base of the skull with the appearance of vertical habitual head support. But that's very hard to understand given the non-bipedal hindlimbs. The anterior foramen magnum is also in Sahelanthropus, and both are in fact more anteriorly placed than almost all australopithecine crania. It's hard to see why these first hominins would be so extreme in this trait, with so few other signs of effective upright posture. I'm honestly puzzled.

First, thanks John, for taking the time to check the comments and respond in un-dumbed-down detail.

I'm honestly puzzled.

That, of course, is what makes you an outstanding scientist and teacher. I'm sure you know that already

Quoting Wonderment: First, thanks John, for taking the time to check the comments and respond in un-dumbed-down detail.

[...]

That, of course, is what makes you an outstanding scientist and teacher. I'm sure you know that already

Second that.