Re: Homo erectus: racial variants of Homo sapiens?
Philip Deitiker (pdeitik@bcm.tmc.edu)
Fri, 17 Jan 1997 18:16:36 GMT
dbarnes@liv.ac.uk (Dan Barnes) wrote:
>>How, what's the evidence. The only contridiction is the believe that
>>the asian HE might have migrated to africa 400 to 200 KYBP to form
>>sapiens.
>I've never heard this theory put forward anywhere. Do you have any refs for it?
In popular magazines this idea has been put forth as speculation.
Since some claim that peking man was more like archaic homo sapiens
compared to toher finds. I don't know that this has ever been formally
intertained though.
>> This new data adds to a number of additional possibilities.
>>1. Asian HE migrated to africa to form HS
>Again not a theory I've heard of.
>>2. Asian HE and african HE were 2 different species (subspecies)
>The only one of these three that I'm aware of. H. ergaster eveolved in Africa c.
>1.9 Ma and migrated to Asia by 1.8 Ma. There is the possibility that some H.h.
>may have left c. 2 Ma.
This new [java] data along with the genetic data would support this.
>> Thus one has an overlap period of
>>15,000 years with absolutely no evidence for hybrid forms. There is no
>>significant 'form' evolution either in the immigrants or in the
>>presumptive population. BTW, if one looks at the java skulls it is
>>blatantly obvious that this skull shape is not within in the range of
>>shapes found in any human population (anywhere). Not even close.
>>There is no evidence that the asian population are hybrids (within the
>>last 30KY) of java erectus and homo. There is no evidence in the
>>fossile record that a fast hybridization occured between JAVA homo to
>>produce asian varients.
>This is the whole point of the MRE theory as shown by Thorne and Wolpoff and
>SE Asia is one of the prime areas that the theory is based on. They have done
>numbers of studies showing links from the H.e. (at sites like Trinil, I think) to the
>archaic H.s. (the Ngandong hominids we are discussing) to the modern
>Australians. I know Lahr has done considerable work to disprove this link but
>this work is criticised in turn. They may not be hybrids but the arguement is that
>they are the ancestors of the modern SE Asians.
This is true, but even if you double the pan/homo branch age the
melanesians are no greater than 110KY distant from other eurasions,
which are no greater than 180 to 240KY diverged from SSA population.
It seems highly unlikely that java or peking man, whose finds date
back well before these ages, can be a strong genetic contributor to
the extant SEA populations.
>>2. Evidence of regional hybridizations which demonstrate the merging
>>of AMH and hominid body forms to produce regional variants.
>There is considerable evidence of continuity between hominids in areas like SE
>Asia - see Frayer et al., 1993 for this and for the DNA analysis that supports
>MRE.
How does the DNA evidence support the MRE? The most isolated
populations of SEA (using std mutation/divergence times) is no greator
than 55KY diverged from eurasion population. Alot has been learned
since 1993 about the gentics of the region and the most recent data
support the hypothesis that the melanesian and australoaborignal
populations arrived ~50KYA, became isolated and underwent pretty much
undisturbed regional evolution. How can anyone intelligently stretch a
55KY divergence time into a 400K or 1MY divergence age. Three studies
say, all but undisputably that the melanesian population is of recent
african origin. Then most revealing paper concerns the homogenity of
asain CD4 intron as a subset of all allelic varients found in africa.
The asian population is most homogeneous. Thus the genetic studies beg
the question, if the SEA/melanesian population undeniably presents
itself as a derivative of the eurasion population no 'great age'
divergence patterns between europeans (which MRE present as AMH/N
mixes) and melanesian (which MRE present as AMH/JE mixes) how was such
a great morhological difference maintained in three populations (HS,
HN, JE). With 'partial' divergence ages >>greater than the defined out
of africa mirgration have significantly contributed to the extant HS
gene pool without leaving some kind of marked genetic signature. When
the CD4 paper came out I calculated this probability using three
populations, and it basically comes to the following.
There is only an 8% or less chance, simply based on gentics and
assuming exclusive genetic drift in the mergent poulations, that two
regional populations could have contributed to regional and not left
evidence of a regional signature.
When the paper on the isolation of melasian poulations came out this
even lowered the chance because genetic drift of mt, ZFY and CD4 in
each poulation would have occured independently.
Simply stated there has to be a rather large defect in the way
scientest estimate divergence times if you want to get the proablitily
anywhere close to 50%. Raising the pan/homo divergence age to 40
million years might do the trick. The other problem is that if one
assumes that the populations in the region were reasonably large
(>2000) inds. then exclusive genetic drift events are not feasable
within the presumptive time frame of last contact (the last 30KY).
Thus, there are a great number of biases which need to be made.
1. that pooulations in both europe and asia remained small after
african emmigration (< 2*medial AMH/N contact age/avg. gen time) for
europe and asia which is reasonably estimated at 10000 inds for asia
and 1500 inds for SEA
2. That as luck would have it both mt, zfy, and CD4 all drifted in
favor of the african derived alleles, in CD4 case without evidence of
recombination. I might add for CD4, <5000 inds and <750 inds sized
popualtions are required, respectively-see 1, for an exclusive genetic
drift event.
3. Just before recorded history began all eurasion populations
'burst' in growth as to mask the prehistoric small size. Otherwise the
allowable exclusive dirft interval shrinks
Such things are intangeble, but based upon what I know about
prehistory, I think that the combinations of population size and age
allow for a very low probablity that all parameters were within such a
small biased range (out of all acceptable ranges) to allow such
genetic signatures to escape detection. If I had to guess I would
estimate the probability at .1 to .01%.
Besides look at what happens in the asian region. We have both
genetic and archeological evidence that AMH leave africa ~100 KYA,
then H neaderthalensis dissappears (within 40KY). We have both genetic
and archeological evidence that a new culture and population moves
into the SAE region ~50KYA many islands are quickly colonized that
were never colonized before and over the next 45KY all isolated
regions are colonized. OTOH, java erectus persists unchanged in the
region for 15KY and then, walla, dissappears.
Philip
|