How ET will force Darwin's theory of evolution to adapt

Consider the classic problem of the origin of the complexity of life we see today. The theory of evolution tells us that organisms evolved from a common ancestor starting from the first, simple life form to more complex ones: Independent genes joined up to form chromosomes, organelles came to be incorporated into prokaryotic cells, and single-celled organisms gave rise to multicellular ones. The trouble is we aren’t sure how this hierarchy came to be. Natural selection doesn’t give us a clear answer as to why the selection pressures for more simple organisms didn’t get in the way of the development of higher level entities. Darwin touched upon this problem in The Descent of Man when he noted how in some cases, selfish behavior advances the survival of an individual, but the opposite action, self-sacrificial behavior, promotes the wellbeing of a group.

One way to solve this would be to take a time machine back to Earth’s early history to observe the development of the biological hierarchy in action. But that’s not practical or likely. A slightly more realistic alternative would be the discovery and exploration of other life forms in the galaxy. Depending on whether body plans of aliens are grouped in taxa even remotely similar to the terrestrial ones, we could judge whether the processes creating the biological hierarchy are universal.

Another puzzle relates to a living being’s capacity to evolve. We know that some things are more flexible and easier to change than others, and that this relative capacity for change isn’t due only to permutations in the genetic script. There are other factors at work including regulatory networks and genome structure, but also the whole system within which the organism evolves. Consider that each major evolutionary innovation opens a larger space for possible variations. For example, before multicellular life appeared, there was only so much that unicellular organisms could do—they could not run, build hives or develop language. In this way, we can speak about all organisms on Earth as constrained by one network of evolutionary processes—a biosphere.