The instincts which shape our motives rest on biochemistry which is programmed for in DNA, but our genetics is no more in control of what we do than an architect's drawing is in control of what happens in a building. Just as the design of a building will channel its potential uses, so our genetic blueprint provides the raw material for instincts. But for any animal more complicated than an insect, those instincts are flexible and adaptable, capable of supporting a great variety of motivations. If they were not, culture would be impossible.
Part of the problem in this regard rest on a wildly outdated belief that all scientific description must rise to the perfect accuracy of clockwork mechanism. The world of creatures is not the world of machines. While very simple organisms like bacteria or insects can have rigid instincts and behave in a programmatic manner in response to chemical signals with genetic roots, from fish and amphibians onwards through the history of life there is an increasing role of experience and learning. The nature vs. nurture debate ended in the recognition that both were important, but this has been a bitter pill to swallow for those hoping for biology to reduce into simple terms.
Part 5 of 23 in the Pentenary series.