In other words, Down syndrome isn't inherited therefore not something evolutionary forces can act on. The only way around that is if the base rate of chromosomal anomaly is heritable, yes?
A species that can produce 1000+ offspring (or more) per mating (with multiple matings per adult lifespan) - like most insects, seaturtles/squids, etc. has little incentive to have high precision/accuracy reproduction.
One that does a small handful (whales, elephants, etc), has a lot of incentive to do so (or self abort early on if there is an issue).
This gets complicated though, because while a single individual in a species which is predominantly r strategy (few offspring), can be ‘more’ on the K side, and vice versa.
And a species which has too much consistency, both genetically and ‘approach’ is very susceptible to inbreeding/mono-cropping issues where a single event/disease can wipe them out, or they can even destroy themselves due to recessive traits.
So there is a general (but diffuse!) evolutionary pressure towards a degree of mutation/error in reproduction in even the most hardcore ‘r’ species (which will necessarily produce a lot of noise/‘wasted paths’) at the species level, alongside a hard evolutionary pressure to reduce it for individuals.
In for example humans. Or elephants. Or whales.
This is also why things like rich/poor, healthy/sick, pretty/ugly, strong/weak, etc. will never go away - they’re outcome distributions along a probability curve due to fundamental different approaches by individual humans due to the necessity of how humans have to be in order for humanity (the species) to survive.
Individuals have strong incentives to ‘tip the scales’ in various ways of course, and societies (at a minimum!) have strong incentives to stop them. It’s why aborting based on gender is illegal in India, for instance. [https://pubmed.ncbi.nlm.nih.gov/7920120/]
Because if everyone had the same attributes in order for everyone to be ‘pretty’ or ‘strong’ or ‘rich’ or whatever, then some hypothetical weight-lifting-infectious-disease (or a famine, or an attack by jealous anti-weightlifters) would wipe out the whole population. And if everyone optimized for ‘rich’ genes (whatever that means), then society would implode, because that literally couldn’t work.
And those types of situations, albeit less light hearted, have, do, and will continue to happen eventually.
Think r/K evolutionary strategies [https://en.m.wikipedia.org/wiki/R/K_selection_theory]
A species that can produce 1000+ offspring (or more) per mating (with multiple matings per adult lifespan) - like most insects, seaturtles/squids, etc. has little incentive to have high precision/accuracy reproduction.
One that does a small handful (whales, elephants, etc), has a lot of incentive to do so (or self abort early on if there is an issue).
This gets complicated though, because while a single individual in a species which is predominantly r strategy (few offspring), can be ‘more’ on the K side, and vice versa.
And a species which has too much consistency, both genetically and ‘approach’ is very susceptible to inbreeding/mono-cropping issues where a single event/disease can wipe them out, or they can even destroy themselves due to recessive traits.
So there is a general (but diffuse!) evolutionary pressure towards a degree of mutation/error in reproduction in even the most hardcore ‘r’ species (which will necessarily produce a lot of noise/‘wasted paths’) at the species level, alongside a hard evolutionary pressure to reduce it for individuals.
In for example humans. Or elephants. Or whales.
This is also why things like rich/poor, healthy/sick, pretty/ugly, strong/weak, etc. will never go away - they’re outcome distributions along a probability curve due to fundamental different approaches by individual humans due to the necessity of how humans have to be in order for humanity (the species) to survive.
Individuals have strong incentives to ‘tip the scales’ in various ways of course, and societies (at a minimum!) have strong incentives to stop them. It’s why aborting based on gender is illegal in India, for instance. [https://pubmed.ncbi.nlm.nih.gov/7920120/]
Because if everyone had the same attributes in order for everyone to be ‘pretty’ or ‘strong’ or ‘rich’ or whatever, then some hypothetical weight-lifting-infectious-disease (or a famine, or an attack by jealous anti-weightlifters) would wipe out the whole population. And if everyone optimized for ‘rich’ genes (whatever that means), then society would implode, because that literally couldn’t work.
And those types of situations, albeit less light hearted, have, do, and will continue to happen eventually.