But we must also recognize sex isn’t just about reproduction, in some species (particularly humans) it is used for bonding and social purposes, and even for commercial and political control.

Sex and gender plays an important role in evolution and natural selection, but how it manifests itself is capable of infinite variety. Remember Spock’s “Amok Time”? And what about that old sci-fi flick “Mars Needs Women”?

From what I understand many other mammals have sex for pleasure. A significant number of species engage in oral sex. Not sure about non mammals. I would be surprised there aren’t aliens out there somewhere in this vast universe who enjoy sex for the fun of it too.

Any aliens coming here to take our chics would definitely mean interstellar war! lol

Nivens’ (Or was it Pournelle’s?) “Moties” were not bilaterally symmetrical. Bisexuality is common, but there are many other alternatives, even on earth. There are hermaphrodites, asexual reproduction, sexual alternation, or specialized sexual castes (as in social insects). Even among higher mammals with conventional sexual/reproductive equipment, sometimes reproduction is restricted to the alpha male and female (as in wolves). The only truly common and universal sexual strategy I can think of is that there are never MORE than two sexes. More than two probably interferes with the statistics of natural selection.

I suspect we may find alien sexual practices quite disgusting (and vice-versa). Then again, they may use a sexual prosthesis and have developed some technologically-assisted form of reproduction.

Pierson’s Puppeteers have a third sex, but it is not really a sex at all. It is a different (non-sentient) species altogether which they have domesticated and in which they deposit their eggs and upon which the larvae feed after hatching. A lot of insects on earth do this.

Like I said. We should be ready for anything.

But even jellyfish have sensory organs. Eye “spots” that allow them to sense light and even see prey. A mouth to consume with.

I think it likely any alien life would have sensory organs for sight, smell, sound, taste, touch, even if they are much different from ours, as is the case with many other species on earth.

We know some similar structures have evolved independently, like eyes, both molluscs and vertebrates have similar optical sensors. But others, like the lateral lines of fish and insect antennae, are very different to how mammals are equipped. Many creatures can navigate a universe of olfactory gradients!

I don’t doubt there will be some aspects of alien biology and behavior that will be familiar, but there will also be others that are totally unexpected.

But I also expect that whatever weirdness we do encounter, there will be some life form on earth that has adopted a similar strategy. Similar problems will be handled by similar solutions–but not necessarily. And I suspect that the social organization and behavior of aliens will be radically different from ours, even if their anatomy, physiology and chemistry is not. Cooperative technical intelligence only arose in one species on our world. That doesn’t give us many examples to compare and contrast.

Science fiction has done an excellent job of speculating about alien biologies, psychologies and cultures. Some of these speculations may be off the mark, but its still a good place for astrobiology weenies like us to look for ideas.

Certain biological traits lend themselves more to tool making than others. Specifically the opposable thumb. Tenticles and elephant snouts are not as up to the task.

The universe is vast, and aliens would undoubtedly be very strange, but it seems unlikely to me that we are the only species in the universe that would exhibit the biological traits earthlings have.

I do better using a format like the one I used in the archeology story I posted here like 18 months ago… the one with the octopus… told from a gods=eye view.