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Darwin-L Message Log 7:60 (March 1994)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.


<7:60>From princeh@husc.harvard.edu  Thu Mar 17 14:53:44 1994

Date: Thu, 17 Mar 1994 15:05:20 -0500 (EST)
From: Patricia Princehouse <princeh@husc.harvard.edu>
Subject: Re: Time article
To: darwin-l@ukanaix.cc.ukans.edu

	I'm glad Jon Marks finally pointed out the most glaring error of
the _Time_ piece ("Anthropopithecus" obviously their fact checkers were
down that day...). Otherwise it is not the worst popular article to come
out recently. However, there is the error of having it at all.

	Recall that the argument for "out of Africa" sees _H.s.s._ as
arising in Africa @200kya. Everybody accepts that _H.e._ was in Java at
least 800kya and as John Langdon pointed out there have been suggestions
before that the fossils were perhaps as old as 1.2 or 1.4 my. The 1.8my
date, even assuming it's good (that is, assuming that the fossil wasn't
redeposited in older sediment at some point, an occurance more common
than anybody wants to think about), doesn't change anything.

The date makes ABSOLUTELY NO DIFFERENCE WHATSOEVER as far as the African
vs multiple origin debate goes.

	It puzzles me greatly as to why _Time_ chose to make such a big
noise about it. I'm afraid it's a sort of tabloid stunt. They sort of
imply that since _Homo erectus_ in Asia is 1.8 and the oldest "African H.
erectus" (more and more called _H. ergaster_ because it does not have the
diagnostic characteristics of the species as named in Asia -other than
brain size, that is.) is also 1.8my then the spread might have gone either
way -ie in spite of 4 my of hominid fossil record in Africa, our immediate
ancestors might have somehow arisen in Asia and migrated to Africa. They
don't take it far enough to conjecture whether erectus arose in Asia by
spontaneous generation or by springing whole from the brow ridge of some
local diety.

	Of course the Chinese 200ky "H.s." skull is mixed up in all this
but it's never made clear that this skull looks like erectus with a big
brain -not like you and me and the African _H.s.s._ fossils.

Bayla Singer asks good questions which deserve answers. I think the most
important things to bear in mind are:

1) one migrant per generation is enough to prevent speciation in animals
generally

2) geographic isolation does not necessarily lead to genetic
incompatibility no matter how much morphological change takes place and no
matter how many loci are fixed for different alleles.

Really strong reproductive isolation comes from large rearrangements of
the genome such as changes in chromosome number or large or multiple or
important inversions which make reproduction impossible.

	We can't go back and see if _H.e._ in Asia could produce fertile
offspring with "H.e." in Africa 1.8 my ago. So, we guess -based on what
we know about living and fossil primates.

	The Asian _H.e._ has distinctive morphological traits not shared
with other hominids, so, many people feel they were a distinct species,
even at the level of reproductive isolation. As such, they could not be
the ancestors of _H.s.s._ along with the ones in Africa. However, this
entails assuming that increase in brain size is a convergence between our
line and theirs.  How reasonable is this? Well, brain size increase is one
of the more common trends in all mammal lineages in the past 50 my. And it
certainly happened independently in our line and the robust
australopithecus line (black skull @ 400cc, later ones up to 550cc).  So,
why not. It seems the most parsimonious explanation to me.

Sorry to be so long-winded.

Patricia Princehouse
Princeh@harvard.edu

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