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WHY CAN SOMEONE'S SMELL TURN US ON?
Someone's natural scent is part of their attraction, but it's all to do with a rather unromantic reason - disease.
An alluring smell is a sign that your loved one has an immune system that's different from your own. Combining the two improves your potential children's chances of survival because they will have double the power to fight off disease and infection.
WHY DO WE GO TO WORK WITH A COLD?
Diseases are programmed to reproduce and infect new hosts. Some are carried by other creatures like malaria-bearing mosquitoes.
Others, like cholera, travel through water, but the common cold just needs close contact with others to spread.
If the illness left you too ill to move you'd stay at home and not mix with people, meaning the disease couldn't be passed on to new victims.
Instead, Moalem says, it makes you sick enough to sneeze and cough but well enough to go to work or school.
WHY ARE GREEKS HAIRIER THAN AFRICANS?
Thick hair on arms and legs may originally have protected people against mosquitoes carrying malaria. In Africa, with its intense heat, thick body hair would have been a disadvantage and people evolved having less and less.
Thickest body hair is found where malaria is common and not too hot - the Mediterranean.
HOW DO SEXUAL DISEASES SPREAD SO EASILY?
Researchers are discovering that many diseases can affect behaviour, and it's thought that STDs (sexually transmitted diseases) may influence sexual activity.
Herpes is one that may heighten sexual feeling because it can make the area itchy and increase awareness of it. That's liable to increase a desire for sex that the virus welcomes, as it's programmed to survive and reproduce, and this increases the likelihood of being passed on.
WHY DO CERTAIN RACES GET DRUNK MORE EASILY THAN EUROPEANS?
In Europe in ancient times people purified water through fermentation to make beer, and the alcohol in that process killed microbes.
In the Far East, people purified boiling water only to make tea, so did not build up a tolerance to alcohol. Unlike Europeans, they do not produce.
