We certainly did not evolve to become bankers and dress designers. As far as anyone can tell, the pressures we had to defend against were infections, predators, murder (ancient and common), and starvation, with suicide and childbirth somewhat lower in incidence. Accidental deaths by falling and drowning must have been noticeable, particularly for children.
The prehistoric world, in other words, provided fertile soil for defensive emotions like fear and anxiety. Emotions, regulated by an expanding brain, were successful in dealing with ancient threats—and modern ones, too, since our brains stopped expanding and longevity reached a plateau.
Growing up, most of us hear patchwork explanations of our behavior—why we resemble Mom and Dad not only in looks and disabilities but in our behavior. Eventually we hear that our inheritance reaches even further back, to the cave man and woman. To anyone with some biological grounding, the principles of evolution and genetics may appear to permit limited inferences about the transmission of behavior. Unfortunately, confusion and colorful speculation has jumped ahead of scholarly chin-scratching with loads of paleobunk, ascribing healthy diets, political orientations, and gender roles to the newly-mutated genes of our ancestors.
BIO: Clearly humans have not always existed in their present form. There’s the fossil evidence to consider. Neither did we flash into existence all at once, or why would we have reflexes found in much more ancient organisms?
Psychology rests upon the theory of evolution, and it’s an important part of an education in psychology. Nowadays, websites try to boil it down to four key principles or four main themes or even 10 basic steps. Thorough immersion is better.
The evolutionary path from hominids to hominins to modern humans isn’t a mountain-climb when you just want to get the big picture in mind. Don’t be put off by trustworthy materials that aren’t in scientific journals if you just want a quick recap. Just beware of claims that evolution has an agenda, or that it always proceeds from primitive to complex.
PSYCHO: Evolution is a change in the distribution of genes in a biological population. Anatomy and physiology can certainly evolve because the path of gene actions to the resulting phenotype can be traced.
Can behavior evolve? There is not a one-to-one relationship between genes and behavior, and we are unlikely to find a gene “for” a complex behavior. Genes are often pleiotropic and behavioral traits tend to be polygenic. Yet there are species-typical forms of behavior and behavior sometimes changes with gene mutations. There are links from genes to behavior that can be tested against natural selection. They can be identified for groups more easily than in individuals with heritability estimates (short story or long story).
But this is not to argue the evidence for “nature” against evidence for “nurture”. The nature-nurture controversy is built on a false dichotomy. Genes and environment are always interactive. Writers who argue that genes force us into types of behavior abuse the concept of evolution. Other traps await the unwary or uninformed. The frequent presence of genetic effects on behavior is also evidence for the frequent influence of the environment.
Sometimes it helps to break down gene-behavior links into a two-step process: Genes influence neural organization and the nervous system regulates behavior. This brings brain evolution into the investigation of behavioral evolution. However, the evolution of the brain calls for a foundation as thorough as understanding evolution. You can start here, there, or yonder (dealing with brain size) and continue for a decade or so. Be forewarned that the popular question of how we got big brains is just a small part of explaining brain evolution. You might want to start with neurons and hope to end with conclusions about biological influences on cognition, developing a timeline for art, hunting, funerary routines, and religion. Keep in mind the importance of environmental changes.
SOCIAL: The environment includes other people, who form cultures that have guided human evolution starting with the evolution of the brain, which is sometimes called our social brain.
As we evolved, new societies fed back into biological evolution, making cultural evolution not just a metaphor but a case of coevolution. Teasing apart causes and effects has become a puzzle of “what influenced what?” that engages anthropologists as well as psychologists.
We evolved in a cultural matrix in which biology and culture both supplied the nature and the nurture of our development, exemplified by the Baldwin effect and epigenetics (video here). These ideas have been around for a while. Grab them quick before the bestsellers write them into a Punch and Judy show.