One of Darwin's most contraversial and contested conclusions is that by sexual selection through evolution, male humans are superior to female humans.
We may also infer from the law of the deviation from averages... that the average mental power in man must be above that of women.
There are many other statements like this one in The Descent of Man. Modern feminist and gender theory tends to refute this type of thinking in every way.
You might check out this book, by Antoinette Brown Blackwell: The Sexes Throughout Nature was published four years after Descent and takes Darwin to task for focusing on physical struggle instead of cooperation, and assuming that the Male is the Normal while the Female is the Abnormal.