After writing my last post about An Exposé on the Evolution of Women’s Body Hair, I gotta thinkin’…

Much of the whole debate of that topic, and any topic relating to how humans behave, comes down to the argument of cultural vs. biological evolution. 

Humans have a convenient capacity to store and transmit culture to each other and successive generations, which other animals don’t appear to be able to do.

Michael Tomasello uses the ratchet effect as a metaphor of how human knowledge is cumulative and thus when new information or technology is passed down, the ratchet goes up a notch.

The problem of this peculiarity of humans is that it makes it a hard feat to determine what human behavior is cultural and what is biological. 

And finding a culture-less human is near impossible, lest you run into a feral child raised by wolves. But even then, would they perhaps pick up the “culture” of the wolves themselves?

I guess we can ask Princess Mononoke


mogul jungle book

Or Mowgli?


Perhaps it is a biological imperative that humans adopt the culture that surrounds them.
It seems there is no way to untie the intertwining threads of culture and biology when it comes to humans.

Well, apparently there is a theory that attempts to reconcile these two types of evolution, and that is the dual inheritance theory.

Dual Inheritance Theory (DIT)

Dual inheritance theory claims that humans unique ability to acquire and pass on culture is in itself a biological adaptation. It is presumed that at some point in our biological evolution (before our human ancestors had what we would consider a “culture”) social learning which lead to cumulative cultural evolution became biologically advantageous. The ones who could, for example, communicate with each other about the saber-toothed tiger which comes every late evening from the forest near the lake, perhaps were better fit to survive. 

Those humanoids (I say humanoids instead of humans because it is unclear when this cumulative culture ability first arose, Homo sapien?, Homo erectus?, Homo hablis?), who had this capability had higher chances of survival, and thus could pass on this information as well as whatever genes were necessary for this kind of social learning mechanism. This social learning process gave rise to cultural evolution, running in tandem with bio-evolution.

In essence, they are inextricably linked, having a continued effect on each other.

While culture can constrain our biological imperatives, it does not override it completely. If someone has a faulty gene that will give that person a higher chance of becoming an alcoholic, in the right prudent environment such a tendency may be impeded. Nevertheless, that person would still have a higher chance of becoming an alcoholic than a person without such a faulty gene, given certain circumstances (being surrounded by drinkers) were to befall them both.

Likewise, our biological makeup in some instances can be affected by our cultural evolution. As humans started to raise cattle for meat, we also started to indulge in their milk. Originally, humans were not fit to drink cow’s milk, and in fact there is still a great proportion of humans who are lactose intolerant. A gene-cultural evolution (mostly taking place originally in Northern parts of Europe) is suspected for this adaptation.

But there are also suspected maladaptations which occurs during this interacting mix of genes and culture. For example, eating disorders, and indeed the previously mentioned alcoholism tendencies, can both be considered maladaptations. However, Dual Inheritance Theorists posit that there are no real maladaptations, rather the person(s) are simply not suited for that environment. To these theorists, any maladaptation is a potential beneficial adaptation, given the right environment. In fact, it has been suspected that this alcohol gene became more prevalent among isolated groups of people who were subject to harsh conditions such as famine and malnutrition. For example the Irish have been known to be put under tremendous pressure by famine and lack of native meat sources. At the time, this gene helped the Irish absorb more iron. That plus constant subjugation by the English made some Irish who had these mutated genes better fit to survive. The fact that Ireland and all industrialized nations no longer have such food shortages in the modern era, and the fact that alcoholism is debilitating and looked down on, is what makes this gene “maladaptive”. 

So, DIT does really nothing to unravel the entwined inheritance systems, but shows in the case of humans, the untying can not be done. The reconciliation that can be found here is that it is impossible to pinpoint (in many cases) which evolutionary changes are due to culture and which to bio-genetics. 

SOURCES:,, ScienceDaily, NCBI,,