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> And then there is the realisation that this is a population-specific, not species-specific, trait! It is a bit of locally acquired genetic knowledge. Some hu
by guard-of-terra 10y ago
> And then there is the realisation that this is a population-specific, not species-specific, trait! It is a bit of locally acquired genetic knowledge.
Some human populations "know" how to digest milk, and some don't. Non species-specific. It's a bit of locally acquired "genetic knowledge" as well.
What's surprising here?
- thaumasiotes 10y agoAll human populations "know" how to digest milk. We're mammals. What differs is whether we stop digesting milk, not whether we know how in the first place.
- guard-of-terra 10y agoI don't see how it affects my line of reasoning. All spiders can see eggs in the fangs of their opponents. What differs is whether they react to it.
- undersuit 10y agoBecause humans that can consume milk are actively expressing genes that process lactose. Those genes are expressed in mammalian young, and adult humans who are lactose tolerant. To say that adult lactose digestion is similar to Portia's egg sac spotting abilities is to say that all spider's have an egg sac spotting gene and it's only expressed in the Portia species in a specific geographical area. Maybe, but then we have an issue with the rest of spiders. If spiders have an egg sac spotting gene, is it inactive during certain times? Actually you may be onto something, being able to spot an egg sac would be useful for a male to determine the receptiveness of a female to mating. Maybe the Portia spiders in the specific area have a mutation so they are always looking for egg secs, instead of just when a male is looking for a mate.
- guard-of-terra 10y agoYou're missing my point. My point is that evolution happens in a subset of whole population. Sometimes it goes so far that a new species are created. So, different populations of same species are expected to have evolved different subtle traits. I don't think that Portia too carry eggs in their fangs. Nothing points to that as I recall.
- undersuit 10y agoYou're missing my point, maybe because I veered off into musing on how an egg sac detection trait could be a gene. I'm trying to say that the development of what almost looks like a learned behavior but is possibly a geographically isolated gene is more surprising than the modification of a gene so that it is expressed past childhood. We see the latter all the time in other forms if you look at domesticated animals as we have selected for the cute and cuddly traits for adult animals that are normally present in infant forms.
- pvaldes 10y agoIn fact is more complex than the article says, because Portia do not only eat other spiders. They also steal preys of other spiders and also eat an appreciable amount of spider eggs; egg sacs are a resource. Therefore "spiders with egg sacs can't attack me" is only one of the explanations. Another could be: "spiders with egg sacs worth the extra effort because is two meals for the prize of one", "spiders with egg sacs are starving and are easier to attack", and even "that spider just have some kind of round prey in its mouth currently, so should be well feed and have enough fat to create my own egg sac". To claim that "that animal is thinking X" you need to discard or at least discuss all possible alternatives. Is very "annoying" when you design a experiment, because maybe you just do not have the money to cover other interpretations, and some kind of experiments have more possibilities to be funded than other.
- ommunist 10y agoTry digesting milk after antibiotic course. We are mammals only by birth.
- deleted 10y ago[deleted]