How can we explain modern humans?

What is the relationship between culture and biology in humans?

Culture can be best described as a learned social system consisting of our structure, behavior, and beliefs. As humans we live in a society mediated by culture. In an attempt to understand our evolution through biology we have to consider our culture as well.

Humans in general have a highly developed ability or capacity for symbolic thought, invention, and learning. But we also display learned social representation, and anticipation of social facts and norms. All of these could fall under the umbrella of human culture. The relationship between human culture and human biology converge and overlap. Culture determines how one will be influenced by and react to the environment surrounding them. Biology affects culture almost naturally. Our biology is fundamental to our existence. It defines who we are chemically and how we function as human beings. Culture and biology are basic properties for life. That is why to understand one you must understand the other. 

 (http://anthro.palomar.edu/synthetic/images/map_of_sickle_cell_frequencies.gif)

What situations exemplified how this works?

• One example of how the relationship between culture and biology works is malaria. In WWII, the World Health Organization started spraying DDT, this killed off the majority of the mosquito population that were not resistant to the chemical. Consequently, the mosquito's that were resistant to the chemical were able to reproduce and pass on the resistance to their offspring. This created a generation of resistant mosquitoes. In an attempt to fight malaria, the use of DDT shrunk the population of mosquitoes temporarily but also led to a platform for stronger new mosquitoes who are now immune to the disease. The homozygote with sickle-cell traits didn't allow the person to survive and those that did not have sickle-cell alleles and were infected with malaria could not survive either.
  Subsequent to the rise of malaria, many died of this disease. Although, those with the heterozygote trait that produced some abnormal hemoglobin had an advantage. And the surviving population passed on this advantage. This exemplifies the variety between culture and biology and how you cannot get rid of one problem without creating a new one (Jurmain, pg. 319-320).

• Relative to human biocultural evolution, lactose intolerance is not found in all adults but many. The ability to digest milk in infants and babies is normal. Around the age of ten, humans ability to digest lessens. There are many factors to consider with the ability to digest milk. Geographically, some Africans and Europeans are lactase persistent, and many other African and Asian populations are lactose intolerant. Lactase persistence is relative to the historical cultural dependence of milk (Jurmain, pg. 319-320).