[ExI] The ugly Neanderthal
rafal.smigrodzki at gmail.com
Sat Dec 12 10:01:14 UTC 2020
On Wed, Dec 9, 2020 at 3:47 PM Dan TheBookMan via extropy-chat <
extropy-chat at lists.extropy.org> wrote:
> On Dec 9, 2020, at 12:33 PM, Anton Sherwood via extropy-chat <
> extropy-chat at lists.extropy.org> wrote:
> On 2020-12-08 23:19, Rafal Smigrodzki via extropy-chat wrote:
> "The Goodness Paradox" by Richard Wrangham offers the opposite perspective
> - Neanderthals were untamed, violent, reckless and dangerous. We know that
> because their skulls do not show signs
> of the domestication syndrome. [...]
> I recently enjoyed that book.
> I wonder: if you were to repeat the Belяev fox experiment, but selecting
> for some irrelevant feature of the domestication syndrome (e.g. white
> spots) rather than for tameness, would tame animals result?
> IIRC, it’s sort of the accidental linkage between certain genes
> controlling development parts of the brain with those for other traits such
> as ear shape and coloration in mammals. Probably stuff on the same
### It's more complicated. Being on the same chromosome results in genetic
linkage. There are many cases in selective breeding where a desired trait
is genetically linked to irrelevant or deleterious traits, and it may take
many generations of breeding to break the linkage but this is different
from the domestication syndrome.
Domestication is brought about by changing a neurodevelopmental program,
which involves hundreds of genes on different chromosomes. In the course of
individual development an animal must behave differently depending on the
phase of development it is in. In infancy and childhood it must be gentle,
inquisitive, non-threatening, playful, appeasing, cute, uninterested in
sex, uninterested in competing for positions in the hierarchy, to be able
to avoid setting off lethally aggressive behaviors in adults, to build
lasting friendships where possible, and to learn about the world. Baby
animals are too physically weak to afford being mean. As they mature and
gain physical strength and experience, they are able to fend for
themselves, which means they have to compete for food and can also afford
reproduction, which means they need to compete for mates, which means they
have more to gain from being assertive and aggressive. There is a whole
symphony of physical and psychological changes during puberty that
coordinates hundreds of genes but there is only a small number of master
switches that control the timing and general direction of the program.
Sexual maturity in the sense of being able to generate gametes and to breed
is a part of this process but the developmental program goes far beyond
simple sexual maturity.
Domestication occurs when these master switch genes are dialled back to
keep the individual from developing full adult features, while still
allowing sexual maturity to proceed. Since there are only a few master
switches that control the transition to adulthood, mutations affecting
these switches will have pleiotropic effects, regardless of chromosomal
linkage. For example, we know that some features of the domestication
syndrome are related to neural crest cell migration, and these cells are
involved in many processes - such as producing skin coloration and setting
up neuroendocrine organs. Selection for tameness means selection for
reduced fear and reduced aggression, which means selection against the
development of the hormonal systems that trigger aggression and fear - for
example the adrenergic system which depends on the neural crest cells. This
means selection for tameness selects for weaker neural crest cell
migration. Since neural crest cells also control skin pigmentation,
weakening of neural crest migration often produces defects of coloration,
such as white spots on horses and dogs. This is why domesticated animals
are often both tame and spotty.
As more research is done we will know the exact loci for the desirable
traits of domestication. People and nations so inclined may then decide to
direct further evolution of these traits by embryo selection.
Finally, peace will reign, when no more assholes are born.
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