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I am curious as to how complex behavior is passed down genetically? For example, how is the building of a web genetically coded in a spider? And how is the complex behavior of constricting prey coded into a boa? As these critters do not get raised by their parents, and hence cannot learn to copy these behaviors, it has to be genetically imprinted. How?

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    $\begingroup$ Some will probably be genetic, yes, but many will be learned. Just like you learned from your parents and will teach your children. What makes you think that any learned behaviors are passed down genetically? They might be, perhaps through some form of epigenetic modification, but it's unlikely to be very common. $\endgroup$ – terdon Jun 4 '15 at 10:28
  • $\begingroup$ user1894167 - I edited your post as it contained inconsistencies as rightly pointed out by @terdon. If, however, this edited version no longer reflects your original question, please feel more than free to roll back. However, in that case additional edits are recommended, as your original question was confusing. $\endgroup$ – AliceD Jun 4 '15 at 10:45
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    $\begingroup$ There can be whole books written on this topic and we wont still have answered this question. How instincts are genetically coded is still under research. For some there is an answer. Therefore I ask you to narrow down to a specific case. $\endgroup$ – WYSIWYG Jun 4 '15 at 11:25
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    $\begingroup$ @AliceD primitive instincts like fear can be explained based on epinephrine signaling. But web-spinning and all are much more complex and you very well know that we don't know the answer to these complex instincts and these are actively being researched upon. This is one of those unanswerable questions :P $\endgroup$ – WYSIWYG Jun 4 '15 at 12:03
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    $\begingroup$ thanks for the edit Alice. I think you phrased it better. $\endgroup$ – Anoop Alex Jun 4 '15 at 12:29
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I will focus my answer on the evolution of orb web spiders (Fig. 1), because arachnids, like insects, are relatively non-complex creatures with an obvious systematic behavior (the weaving of highly symmetric, repeating structures). Hence I reasoned this would be a good approach of investigating the answer to this question.

The orb-weavers (Orbiculariae, an informal name for the taxon containing the superfamilies Deinopoidea and Araneoidea) are among the most diverse lineages of spiders (Hormiga & Griswold, 2014).

Orb
Fig. 1. Orb web. Source: Encyclopedia Britannica

Bond et al. (2014) report that according to various estimations the date of the origin of the orb web was somewhere around the Lower Jurassic 201 million years ago and 52 million years ago, and the authors support the view of a monophyletic origin of the orb web.

Despite this excellent opportunity to elucidate the (monophyletic) genetic underpinnings of the evolution, and hence the passing down of orb weaving, are largely unknown. Not only is the evolution of orb weaving unknown, even the evolution of the intricate physical properties of the silk are largely unknown. For example, how the sticky glue araneoid orb web evolved is a mystery. This complex multicharacter trait is hypothesized as a key innovation to explain the increase in diversity of araneoidea. For example, araneoid orbs contain viscous adhesives and they have low UV-reflectance and are hence less visible to insects. There exists one proposed evolutionary pathway from the dry, cribellate orb web of deinopoids to the sticky glue orb web of araneoids, but that's about it (Hormiga & Griswold, 2014).

In all, physical properties of silks contained in webs are hardly explained in evolutionary terms, let alone the behavioral profiles necessary to make a web out of it.

References
- Bond et al., Curr Biol (2014); 24(15): 1765–71
- Hormiga & Griswold, Annu Rev Entomol (2014); 59:487–512

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  • $\begingroup$ I think thenakedscientists.com/forum/index.php?topic=26203.0 is claiming to answer the part of the question re spiders. $\endgroup$ – Anoop Alex Jun 7 '15 at 5:14
  • $\begingroup$ @user1894167 - that link describes arachnid behavior $\endgroup$ – AliceD Jun 7 '15 at 10:50
  • $\begingroup$ well the first post does seem to be claiming a genetic explanation that leads to structured web building in spiders. I'm not saying I believe it since it doesnt cite any sources but just thought I would post an alternative explanation. $\endgroup$ – Anoop Alex Jun 7 '15 at 15:00

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