What evidence do we have that genetics play a role in intelligence?

Intelligence tests were designed based on the belief that there are measurable differences in ability between individuals that can help to predict future performance. There has been a long-term debate on what the word intelligence really means and a more heated debate on how much of intelligence is a product of nature (genetics) and how much is contributed by nurture (environment). In this discussion, we will explore the arguments for each of those influences.
As you create your discussion post, consider the following:
What is intelligence?
What evidence do we have that genetics play a role in intelligence?
What evidence do we have that environment is also involved?
Over the last hundred years there has been a great deal of discussion and research that has tried to determine the relative influence of nature and of nurture on intelligence. The consensus today is that both make a strong contribution. Find one piece of evidence showing that nature (genetics) makes a contribution and one showing the influence of nurture (environment). Describe each of these pieces of evidence and explain why it supports the influence of either nature or nurture, as appropriate. What is the practical importance of understanding that intelligence is influenced by both factors?