Passage Three Archaeology can tell us plenty about how humans looked and the way they lived tens of thousands of years ago. But what about the deeper questions Could early humans speak, were they capable of self-conscious reflection, did they believe in anything Such questions might seem to be beyond the scope of science. Not so. Answering them is the focus of a burgeoning field that brings together archaeology and neuroscience. It aims to chart the development of human cognitive powers. This is not easy to do. A skull gives no indication of whether its owner was capable of speech, for example. The task then is to find proxies (替代物) for key traits and behaviors that have stayed intact over millennia. Perhaps the most intriguing aspect of this endeavor is teasing out the role of culture as a force in the evolution of our mental skills. For decades, development of the brain has been seen as exclusively biological. But increasingly, that is being challenged. Take what the Cambridge archaeologist Colin Renfrew calls “the sapient (智人的) paradox (矛盾)”. Evidence suggests that the human genome, and hence the brain, has changed little in the past 60,000 years. Yet it wasn’t until about 10,000 years ago that profound changes took place in human behavior: people settled in villages and built shrines. Renfrew’s paradox is why, if the hardware was in place, did it take so long for humans to start changing the world His answer is that the software – the culture – took a long time to develop. In particular, the intervening time saw humans vest (赋予) meaning in objects and symbols. Those meanings were developed by social interaction over successive generations, passed on through teaching, and stored in the neuronal connections of children. Culture also changes biology by modifying natural selection, sometimes in surprising ways. How is it, for example, that a human gene for essential vitamin C became blocked by junk DNA One answer is that our ancestors started eating fruit, so the pressure to make vitamin C “relaxed” and the gene became unnecessary. By this reasoning, early humans then became addicted to fruit, and any gene that helped them to find it was selected for. Evidence suggests that the brain is so plastic that, like genes, it can be changed by relaxing selection pressure. Our understanding of human cognitive development is still fragmented and confused, however. We have lots of proposed causes and effects, and hypotheses to explain them. Yet the potential pay-off makes answers worth searching for. If we know where the human mind came from and what changed it, perhaps we can gauge where it is going. Finding those answers will take all the ingenuity the modern human mind can muster. The questions presented in the first paragraph ___________.