Re: Date for Last Common Ancestor?

Susan S. Chin (susansf@netcom.com)
Sun, 11 Aug 1996 22:45:54 GMT

Stephen Barnard (steve@megafauna.com) wrote:
: T&B Schmal wrote:
: >
: > I am interested in bracketing the dates for the last common ancestor of
: > humankind. Would a good guess be somewhere between "Eve" and the
: > appearance of modern man - say, between 200 and 50 Kya? It seems to me
: > that dates outside this range would be impossible.
: >
: > Is this on track and can this range be narrowed? Suggestions welcomed.
: >
: > Tom Schmal
:
: The attribute of being "the last common ancestor of humankind" has a
: very peculiar property. That person can only be identified long after
: the fact, and the identity and date of that person is liable to be
: changed radically at any time. For example, if a new disease were to
: decimate the world's human population, with only say 10% of the people
: surviving because of an inherited resistance, then the date of the last
: common ancestor would probably be moved forward in time considerably.

: Steve Barnard

Whether or not we will ever determine who and when this last common
ancestor occurred, I don't see how it can arbitrarily be moved forward in
time due to a scenario of catastrophic decimation of 90% of humankind. The
assumption is that by that time, the LCA had already split off to form
these various populations.

Even if you subscribe to the theory of multiple and separate evolutionary
roots of mankind per geographic regions, at one point, there was
a species of organism from which Homo sapiens sapiens arose.

The "Eve" that we hear about as the "mother of us all" is really a
population which contained the genes which ultimately resulted in all of
humakind as we see it today. It was not meant to imply (though of course
it does anyway) that we all arose from one female individual, but from a
population of individuals with those genes.

The question should be how reliable is the molecular data, and to what
extent should paleoanthropologists rely on it in developing their
theories of evolution and the LCA?

Susan

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                                             susansf@netcom.com