tag:blogger.com,1999:blog-37148773.post6545922251012670902..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Accelerated Human EvolutionLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-37148773.post-59061936702506434132007-12-12T17:27:00.000-05:002007-12-12T17:27:00.000-05:00That is only possible if you have a custom-made de...That is only possible if you have a custom-made definition of fitness. By other definitions, if more descendants are made possible, fitness has increased, no matter how "crappy" the lifestyle may seem.<BR/><BR/>Truth is, in evolution a shift in lifestyle hardly ever can be confidently described as an increase of fitness or "improvement" of adaptation; but simply a shift into a different mode of existence, with other balances and trade-offs (despite popular notions of progressism).A. Vargashttps://www.blogger.com/profile/04876504431768677209noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-70363965382826706992007-12-12T14:56:00.000-05:002007-12-12T14:56:00.000-05:00It's not clear to me why there would be such an ex...<I>It's not clear to me why there would be such an expansion if people were less fit.</I><BR/><BR/>It's known that average stature, life expectancy, and indications of morbidity visible in human remains, all deteriorated sharply after the agricultural revolution (that's what prompted Jared Diamond to quip that it was "the worst mistake in the history of the human race"). Yet, the availability of enough food to feed far more mouths enabled this less-fit population to expand rapidly. So, while remaining agnostic on the conclusions of that paper, I would have to say that the idea is by no means absurd and self-contradictory on its face.Steve LaBonnehttps://www.blogger.com/profile/05315820864846104986noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-18087590608933730922007-12-12T13:53:00.000-05:002007-12-12T13:53:00.000-05:00Dunbar says,I'm not a population geneticist by any...Dunbar says,<BR/><BR/><I>I'm not a population geneticist by any means, but I think a larger effective population size means even slightly adaptive traits have a higher probability of being fixed.</I><BR/><BR/>The probability of being fixed depends on the fixation coefficient (<I>s</I>). It's approximately <I>2s</I>. <BR/><BR/>If a beneficial allele has a fixation coefficient of 0.03—as in many of the examples in the paper—then it has a 6% chance of being fixed in the population. <BR/><BR/>The rate of fixation depends on the size of the population. The larger the population the longer it takes.<BR/><BR/>The biggest effect of population size is the number of mutations. With large populations it becomes increasingly likely that a particular beneficial mutations will occur in a finite amount of time.<BR/><BR/>Hawks et al. say that the conversion to an agricultural society made the existing population less fit so it had to evolve by acquiring more adaptations. Fortunately for us, the population of our ancestors expanded enormously at just the right time. <BR/><BR/>It's not clear to me why there would be such an expansion if people were less fit.Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-66551081928970190362007-12-12T10:30:00.000-05:002007-12-12T10:30:00.000-05:00I'm not a population geneticist by any means, but ...I'm not a population geneticist by any means, but I think a larger effective population size means even slightly adaptive traits have a higher probability of being fixed. I like Hawk's blog, and I find the premise interesting and plausible, so I won't say I'm skeptical. Maybe we should all wait and see?Alexhttps://www.blogger.com/profile/02590604089043425452noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-42481060720037031992007-12-12T01:13:00.000-05:002007-12-12T01:13:00.000-05:00We found very many human genes undergoing selectio...<I>We found very many human genes undergoing selection," says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million genes showing the most variation.</I><BR/><BR/>I would really like to know who wrote that, <BR/><BR/>3.9 million genes... lolGeorgi Marinovhttps://www.blogger.com/profile/11780516566649792265noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-76610619616042192602007-12-11T17:08:00.000-05:002007-12-11T17:08:00.000-05:00We found very many human genes undergoing selectio...<I>We found very many human genes undergoing selection," says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million genes showing the most variation. "Most are very recent, so much so that the rate of human evolution over the past few thousand years is far greater than it has been over the past few million years."></I><BR/><BR/>How does he reconcile dramatically increased selection with a dramatically increased population size over the same period?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-26800547227890714932007-12-11T16:18:00.000-05:002007-12-11T16:18:00.000-05:00Interestingly Greg Cochran was the guy who has sug...Interestingly Greg Cochran was the guy who has suggested that all our chronic diseases are ultimately infectious. This fascinating theory is documented in Paul Ewald's "Plague Time"Wavefunctionhttps://www.blogger.com/profile/14993805391653267639noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-65498472929512332212007-12-11T16:15:00.000-05:002007-12-11T16:15:00.000-05:00I would think that humans will always be evolving,...I would think that humans will always be evolving, if only because bacteria and viruses will always be evolving...Wavefunctionhttps://www.blogger.com/profile/14993805391653267639noreply@blogger.com