55024 reads #14 among articles published in The Conversation by University of Cape Town sourced authors
How the origin of the Khoisan tels us that race has no place in human ancestry
Until recently, the ancient origins, anatomical, linguistic
and genetic distinctiveness of southern African San and Khoikhoi people were
matters of confusion and debate.
They are variously described as the world's first or oldest
people; Africa’s first or oldest people, or the first
people of South Africa.
What they are in fact are two evolutionarily related, but
culturally distinct, groups of populations that have occupied southern Africa
for up to 140 000 years. Their first-people status is due to the fact that they
commonly retain genetic elements of the most ancient Homo sapiens.
This conclusion is based on evidence from specific types of
DNA. This evidence also demonstrates that other sub-Saharan human populations
retain genetic bits and pieces of DNA from non-KhoiSan primordial humans that
pre-date their Out-of-Africa colonisation of the balance of the world.
What is important in the debate on the origins of, and
diversity among population groups of Homo
sapiens is to establish what cannot, and should not, be derived from the
various DNA evidence used to support the KhoiSan-as-first-people
hypothesis. This is that the KhoiSan, or
any other groups of populations of humans, can be assigned to evolutionarily
meaningful "races" - or subspecies in biological classification.
The abovementioned DNA evidence, if interpreted incorrectly,
could be used to support the findings of the "scientific" racial
anthropologist [Carleton S.
Coon]). As recently as 1962, Coon
recognised the KhoiSan as the Capoid race based on the distinctive anatomical
features of the Capoids from those he used to designate the Congoid race. These
include golden brown rather than sepia coloured skin, the presence of
epicanthic eye folds and prominent cheekbones and steatopygia. Indeed, the scientifically correctly
interpreted evidence points quite to the contrary.
Human evolution can be mapped like a network, not drawn like
a tree
If one were to compare the entire DNA genomes from representatively
sampled human populations from around the world, the resulting relationships
would look more like an evolutionarily reticulated chain-link fence. In other
words, a network rather than a tree. This even applies to even purportedly
racially important anatomical features.
This is because human population groups worldwide are highly
homogeneous (99.5% similar) genetically and their anatomical features vary in
an uncorrelated fashion over the landscape.
In fact, these groups are, in evolutionary terms, very
recent entities that have no
biological significance.
The DNA evidence used to discover the human genetic
"footprints" that characterise the KhoiSan, and other diverging populations,
is the same that forensic pathologists use to determine an unidentifiable
corpse’s population group. This process has been popularised on television
shows like CSI
and Bones.
This DNA evidence comes from:
* Y chromosome
polymorphisms inherited without recombination along [male lineages]
* single nucleotide polymorphisms, or SNPs,
from nuclear DNA and
* most especially from mitochondrial
DNA.
Mitochondria are organelles within a cell that have their
own independent DNA, separate from that in the nucleus that determines an
organism’s external appearance, physiology, etc. They are involved with cellular respiration and
nothing more.
Like the abovementioned
polymorphisms, mitochondrial DNA (and especially a component of it called the
D-loop) evolves much faster than the bulk of nuclear DNA. Moreover,
mitochondrial DNA is inherited maternally (since offspring get their
mitochondria from their mother’s egg) and is thus not intermixed with paternal
DNA during reproduction. This allows the
detection of direct , genetically ‘ungarbled’, connections amongst
evolutionarily recently evolved human population groups.
The mistake that some evolutionary genetic anthropologists make is that they ignore the overwhelming balance of evidence that there is no evolutionarily significant racial variation in either genes or anatomy [see How science has been abused through the ages to promote racism – The Conversation -November 20, 2015]. Instead, they focus on these very few bits-and-pieces of DNA that change rapidly (in evolutionary terms). This way they reach distorted conclusions about discernible “races” within the human species.
Why there is only one race: the human race
Recent DNA results used to detect human population
genetic ‘footprints’ is summarised in the article “Humanity’s forgotten
return to Africa revealed in DNA”.
The story it tells is as follows.
About 140 000 years ago human populations from East and/or
Central Africa moved southwards and ‘colonised’ western southern Africa. The
probable nearest living relatives of these source populations are the Hadzabe
people from north-central Tanzania and and Mbuti pygmies
from the eastern Congo.
This migration
gave rise to the present-day San
hunter-gatherers.
Much more recently - about 2000 years ago - there was a
second movement of ‘colonists’ from the north into south-western Africa that
gave rise to the pastoral Khoikhoi people.
This second group of ‘settlers’ carried within its genome it
bits of Eurasian-sourced
- and even some Neanderthal - DNA derived from European humans that had
returned to Africa about 3 000 years ago.
Subsequent to this second colonisation, there was
intermixing between the Khoikhoi and San (giving rise to their close anatomical
similarities), despite the fact that they retained their marked cultural and
linguistic differences.
Much more recently - about 1700 years ago - there was a
third major north-to-south migration, this time by Bantu-speaking, black
Africans into south-eastern Africa. Those ‘settlers’ that eventually became the
Xhosa peoples moved westwards and encountered the Khoikhoi whom they drove
further west and intermixed with genetically.
It is even possible to map one's genetic ‘ancestry’, as
President Nelson Mandela did, indicating that he possessed some KhoiSan
DNA.
The important point is that this evidence should not be used
to assert that these differences (or shared bits of "ancient" DNA)
support the identification of multiple human "races".
In fact, it confirms the assertion by the late founder of
South Africa's Pan Africanist Congress of Azania, Robert
Sobukwe, who wisely concluded that there is only one race: the human race.
Emeritus Prof. Tim Crowe – e-mail timothy.crowe@uct.ac.za – tel.
021-6743835
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