Post by djoser-xyyman on Jul 20, 2019 20:40:15 GMT -5
Population structure and the evolution of Homo sapiens in Africa -
Richard G. Klein july2019
This is interesting because I sort of believe what he proposing that truly modern humans is less than 60000 years old. How did modern humans evolve? What wa sthe scenario? How did the genes come together to "create" modern humans?
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Fossil populations of H. sapiens surely always varied in appearance and
behavior across Africa, and in that sense, they were structured. However,
there is nothing in the fossil and archeological records or in historic
genetics to suggest the kind of enduring structure that encouraged
Wolpoff to propose the multiregional evolution of H. sapiens across Eurasia. There is also nothing to suggest the degree of population continuity
within African regions that Wolpoff observed in different Eurasian
regions. In southern Africa, where archeological observations are particularly dense, they suggest regional discontinuity.
As an alternative to the multiregional model for Africa, I have
proposed here that population reshuffling in the face of dramatic
climatic change produced novel gene constellations that occasionally included one or more in which the additive or cumulative effect
of newly associated genes enhanced cognitive or communicative
potential. Natural selection would have favored the spread of such
a constellation and behavioral or cultural feedback would have
accelerated its eventual fixation in the African lineage that led to
fully modern H. sapiens. Fully modern H. sapiens would then have
dispersed rapidly across Africa, replacing other lineages or transferring its advantageous genes to them. In the absence of aDNA
observations that could support this scenario, it may always remain
speculative, but it would explain the inflection in the African archeological record marked by the appearance of the LSA 50–45 ka, its
nearly simultaneous expansion to Eurasia in the form of the Upper
Paleolithic, and the ability of fully modern Upper Paleolithic people
to swamp or replace non-modern Eurasians.
There is no theoretical reason to prefer my scenario over multiregionalism. However, my idea depends on an empirical issue that we
should be able to resolve—do the LSA/Upper Paleolithic truly mark an
inflection in the archeological record or does archeology indicate that
much earlier Africans and Europeans were capable of LSA/Upper
Paleolithic behaviors but expressed them more rarely or less conspicuously? An important corollary is the question of whether tiny naturally
shaped but perforated gastropod shells that occur occasionally in
MSA sites provide the same kind of evidence for ornaments or jewelry
as the carefully shaped ostrich eggshell beads that occur in nearly
every LSA site where preservation was suitable. Likewise, does the
MSA pigment lump with the most compelling incised abstract pattern,
dated roughly 75 ka at Blombos Cave, South Africa (Figure 5, top),
qualify as art as unequivocally as the early Upper Paleolithic ivory figurine dated to more than 35 ka at Hohle Fels, Germany (Figure 5, bottom)? To me, the answer to both questions is “No,” which is largely
why I think the LSA/Upper Paleolithic represent a marked break from
what went before. Others would answer “Yes” and some would trace
art (or symbolism) even further back in time, to the volcanic tuff “figurine” dated 250–280 ka at Berekhat Ram on the Golan Heights104 or
to a mussel valve with a proposed geometric engraving dated 500 ka
from Trinil, Java.105 More than theory or models, such personal differences in perception may always impede consensus on modern human
origins.
Richard G. Klein july2019
This is interesting because I sort of believe what he proposing that truly modern humans is less than 60000 years old. How did modern humans evolve? What wa sthe scenario? How did the genes come together to "create" modern humans?
=====
Fossil populations of H. sapiens surely always varied in appearance and
behavior across Africa, and in that sense, they were structured. However,
there is nothing in the fossil and archeological records or in historic
genetics to suggest the kind of enduring structure that encouraged
Wolpoff to propose the multiregional evolution of H. sapiens across Eurasia. There is also nothing to suggest the degree of population continuity
within African regions that Wolpoff observed in different Eurasian
regions. In southern Africa, where archeological observations are particularly dense, they suggest regional discontinuity.
As an alternative to the multiregional model for Africa, I have
proposed here that population reshuffling in the face of dramatic
climatic change produced novel gene constellations that occasionally included one or more in which the additive or cumulative effect
of newly associated genes enhanced cognitive or communicative
potential. Natural selection would have favored the spread of such
a constellation and behavioral or cultural feedback would have
accelerated its eventual fixation in the African lineage that led to
fully modern H. sapiens. Fully modern H. sapiens would then have
dispersed rapidly across Africa, replacing other lineages or transferring its advantageous genes to them. In the absence of aDNA
observations that could support this scenario, it may always remain
speculative, but it would explain the inflection in the African archeological record marked by the appearance of the LSA 50–45 ka, its
nearly simultaneous expansion to Eurasia in the form of the Upper
Paleolithic, and the ability of fully modern Upper Paleolithic people
to swamp or replace non-modern Eurasians.
There is no theoretical reason to prefer my scenario over multiregionalism. However, my idea depends on an empirical issue that we
should be able to resolve—do the LSA/Upper Paleolithic truly mark an
inflection in the archeological record or does archeology indicate that
much earlier Africans and Europeans were capable of LSA/Upper
Paleolithic behaviors but expressed them more rarely or less conspicuously? An important corollary is the question of whether tiny naturally
shaped but perforated gastropod shells that occur occasionally in
MSA sites provide the same kind of evidence for ornaments or jewelry
as the carefully shaped ostrich eggshell beads that occur in nearly
every LSA site where preservation was suitable. Likewise, does the
MSA pigment lump with the most compelling incised abstract pattern,
dated roughly 75 ka at Blombos Cave, South Africa (Figure 5, top),
qualify as art as unequivocally as the early Upper Paleolithic ivory figurine dated to more than 35 ka at Hohle Fels, Germany (Figure 5, bottom)? To me, the answer to both questions is “No,” which is largely
why I think the LSA/Upper Paleolithic represent a marked break from
what went before. Others would answer “Yes” and some would trace
art (or symbolism) even further back in time, to the volcanic tuff “figurine” dated 250–280 ka at Berekhat Ram on the Golan Heights104 or
to a mussel valve with a proposed geometric engraving dated 500 ka
from Trinil, Java.105 More than theory or models, such personal differences in perception may always impede consensus on modern human
origins.