When Darwinians labor to reconstruct human evolution, they usually rely on the fossil record and comparative antomy. Of course, there's a circularity to that procedure. You must assume that certain fossils are related to humans in the first place. But let's bracket that for now.
What can we infer about humans or our alleged evolutionary ancestors from anatomy?
i) Eye-placement. Why do some animals have forward-facing eyes while other animals have eyes on the sides of their heads?
The conventional answer is that predators need binocular vision. That gives them depth perception, which they need to perceive prey at a distance, detect camouflaged prey, and chase it. By contrast, prey species need peripheral vision to detect predators that are sneaking up on them.
And, in general, that's probably a good explanation. But how does that explain human eye-placement? Humans aren't natural predators, in the sense that we don't have the standard equipment to be predators. We lack fangs, claws, speed, strength, or venom.
Moreover, according to evolutionary theory, we're not descended from predators.
We became predators because we had the intelligence and dexterity to design and operate weapons–and not because nature designed us to be predatory. Likewise, we domesticated certain animals (dogs, horses) to aid us in hunting. None of that's inferable from human anatomy.
A fallback explanation is that humans are descended from arboreal animals. Our ancestors needed binocular vision to judge depth in jumping from branch to branch. There are, however, some problems with that explanation:
a) Squirrels have eyes on the side of the head.
b) Once we came down from the trees, our eye-placement became disadvantageous rather than advantageous. At that stage of human evolution we were essentially prey species. Extremely vulnerable to land predators.
So why didn't our eyes migrate to the sides of our heads the way the eyes of flatfish migrate to one side, as an adaptation to new conditions?
ii) Humans lack the dental equipment of predators like wolves and leopards. Yet humans enjoy a meat diet when that's available. For that matter, humans eat i pizza, ice cream, chocolate bars. You could never infer human diet from human teeth. Even if we had the teeth of wolves and leopards, we'd still eat pizza, ice cream, chocolate bars. Our dietary behavior isn't inferable from our dental equipment. We eat whatever we like.
iii) Consider a related example. Many human adults drink milk. Not just babies. Now, one might infer that human adults drink milk because we have the lactase enzyme. But isn't it the other way around? We have the lactase enzyme because we drink milk.
The availability of milk is based on domesticating cows and goats. And lactase is an adaptation to a milk diet. For instance, Asians are more prone to lactose intolerance than Caucasians.
So that's a case where you can't infer behavior from biology, inasmuch as the behavior is driving the biology, rather than vice versa.
iv) You'd never know from examining the human face that kissing is a major form of foreplay. That's because the placement of the nose (especially the aquiline Caucasian nose) gets in the way of kissing. Yet we manage to around it.