Thank you very much for sharing this with me.
I am not a scientist (I got a BA in math/cs in 1973 from UT-Austin but it coincided with my radicalization and when I did return to grad school in the 1980s I studied political economy).
The question of who we are, hence of "human nature," is central to any theory of history. As a Marxist, I have been happy to go along with Marx's and Engels' view that we humans are the sum total of our social relations shaped by the prevalent mode of production. As I became interested in ecology crises and reviewed ecological socialist theories, I became aware that they are, despite creativity of the theorists involved, at the end the proposition that capital accumulation undermines the ecosystems. This much was asserted by Marxists well before ecosocialism was coined. Clearly, a theory of history that includes all of nature is required as M&E themselves point out in The German Ideology (1845). But they, like any good scholar, argue that they set these aside to focus on society and social classes. We know what came after: The Communist Manifesto (1848) that provided a class analysis of written history (about 3000 years old) and concluded with the struggle between the bourgeoisie and the proletariat that they argued might lead to socialism. Marx's Capital is an application of historical materialism to the capitalist mode of production. Thus, it too excludes nature to focus on society.
Marx's conception of human nature evolved in his lifetime. But his most enduring view that stamped his materialism and theory of history is the notion I mentioned above: human nature is the sum total of our social relations shaped by the prevailing mode of production.
To my knowledge there has been no significant advances so far among Marxist on any of these issues. In the light of advances in biology, Marxists generally concede that we are a combination of nature and culture. But they still hang in with the Marx's conception noted above.
Thus, human nature is the sum total of our eco-social relations shaped by the dynamic interrelation of three trends: (1) The transhistorical trend which recognizes and celebrates our continuity with other animals, in particular the primates. We are animals, mammals, an evolutionary cousin of the chimpanzee. Therefore, we share certain traits with them. (2) The historical trend of our species, Homo sapiens, that goes back at least 300,000 years, including cultural heritage from earlier Homo genera: We inherited the knowledge to use of fire from Homo erectus who domesticated it 400,000 years ago. And, (3) the trend specific to the mode of production influences, e.g. capitalistically developed global culture today.
I have watched prof. Sapolsky lectures and interviews available on Youtube and posted some on Our Place in the World (a blog I edit and publish for ecological socialist discussion). What I have heard him say is appealing to me: He says and I am paraphrasing it: the brian, genes, culture, and ecosystems evolve together. I find this resonates well with the summary provided above of what I have learned from my readings over the years.
Of course, I am not in a position to enter a discussion of the issue you have raised. Have you written to him with your objection? If so, what was his response? And, even if he made an error of judgement in that case, does that invalidate the summary of his view which I paraphrased above? (I include the lecture where he presents that view below--it is an hour plus long talk)
Thank you again for your response to my question.