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Because humans that can consume milk are actively expressing genes that process lactose. Those genes are expressed in mammalian young, and adult humans who are
by undersuit 10y ago
Because 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.