Kleinman has challenged me to “do the math of the chimp-human lineage,”
since six million years is roughly equivalent to six hundred thousand
generations, and herein I’ll show how it’s far easier to calculate than
he thought. On average, at conception, you start out with 150 new
mutations right off the bat, something Kleinman should be aware of, and
since for the purposes of this calculation six million years = six
hundred thousand generations, we will calculate 150 times 600000 and see
what we get.
150 x 600000 = 90000000
So, knowing that at conception you have 150 mutations right off the bat,
and that there has been roughly six hundred thousand generations since
the LCA of both humans and chimps, we can safely assume a minimum of
ninety million mutations having occurred since then cumulatively in each
generation from the past to the present.
Kleinman’s one pony trick, the so-called “replication issue,” is easily
solved when one realizes we’re dealing with relatively small populations
isolated from each other by both time and space, and hence mutations
could spread far more easily in such small populations than they can in
a population as large as that of modern humans, which for most of
history was also relatively small, having ballooned only in the last 10k
years since the invention of farming.
The Good DrDr may contest this by asking how many of these mutations
were “beneficial mutations,” and as we shall see only the environment
determines whether a mutation is beneficial, neutral, or negative,
something DocDoc contests but is true nonetheless.
Instead they were wiped out by demographic factors, namely small population size and inbreeding. Modern humans helped out by essentially serving as a sort of “sexual distraction,” so then when Neanderthals mated with modern humans the gene flow went to modern human populations rather than Neanderthal populations, ie we swamped them and assimilated them with little conflict involved, and thereby accelerated a process that would’ve eventually killed them all of anyways.
I propose that Australopithecus is to be more accurately considered a chronogenus, similar to how Homo erectus is considered a chronospecies. I mean, Australopithecus already is paraphyletic because it excludes Homo, its descendant genus, and there are human species that display many primitive, australopithecine traits, and many australopithecine species that feature advanced, human traits. So much so in fact that the line between “human” and “protohuman” has been increasingly blurred over the years, to the point we’re having debates over whether something like H. habilis is truly a human or rather an australopithecine proto-human instead.
We know that stone tools were already in use by 3.3 Ma, and that we were already losing our body hair by 3.2 Ma (which surprise surprise indicates persistence hunting), and that australopithecine social structures would’ve been more similar to modern humans than chimps (australopithecines gave birth the hard, human way, rather than the easy chimp way), including that the males took part in raising the young, and that australopithecine couples were at the very least serially monogamous. We don’t know how complex they were, or how much more similar to modern human socials structures they were than to chimps, since so much time has passed between then and now, but we know at the very least the beginnings of everything thought of as “human,” from bipedality to marriage to technology (rather than simple tool use), had its roots in the australopithecines.
Of course, that’s not to mention the extremely early migrations out of Africa that lead to the H. floresiensis lineage, since recent phylogenetic analyses indicates the Hobbits of Flores were even more basal than H. habilis was, and the findings of stone tools in China dated to over two million years ago, and how the primitive species H. naledi was found to have lived as recently as 200kya, we now know the story of human evolution is a *lot* more complex than we once thought, indeed it’s apt, if somewhat crude, to call it what it is: a *clusterfuck*.