I describe the phenomenon this way. These influences are dynamic, which is to say that they exist not in isolation but in relation to one another. Biology impacts development, which influences culture, which molds development, which conditions biology, etc. Evolution is the result of these dynamic relationships over time. Though I generally don't like mechanistic comparisons between computers and human beings, I have found the following analogy to be useful in explaining these concepts, especially to employees and managers in high-tech companies.
Biology is human hardware.
The hardware can do only what it was built to do. It can do less but not more. This productivity takes place, however, within the confines of an operating system, which, in human terms, is culture. Culture is the template, or operating sytem, that allows the software to run on the hardware. Just as biology restricts what humans can do, culture restricts what humans allow themselves to do with the biology and development that we have.