Why don’t vultures get food poisoning from eating rotten meat?

The acid in vulture’s stomach is almost 10 times as concentrated as ours. This destroys bacteria so efficiently that vulture droppings are actually more hygienic than the meat they eat! But a strong stomach isn’t  enough by itself, because once bacteria have multiplied in a decaying carcass, they release chemical toxins that aren’t destroyed by acid. To counter this, vultures absorb the toxins directly through the lining of their throat and then neutralize them using antibodies present in the blood.

Is the rate of human evolution increasing with population growth?

Larger populations create more chances for genetic mutations to occur, and this means more variations for natural selection to either favour or weed out. But in big populations, it takes longer for chances to spread. The fastest rate of evolution occurs when a population is split into isolated subgroups that can’t interbreed due to geographic or cultural barriers. Travel and communication have broken down many barriers, so our genes get blended together instead of splitting into subspecies. A 2007 study found that we are evolving about 100 times faster than at any other period in our history. But ‘modern’ for an evolutionary biologist means the last 5,000 years. It’s too soon to tell how our evolution has been affected by the population explosion of the last few centuries.

Why does time appear to go fats when you’re asleep?

Does it? Generally this is not true, and most people are good at judging how many hours they’ve slept. Some can even tell themselves to wake up at a specific time and do so. Time perception can be distorted, though, and experiments show that estimates are generally good, but people tend to overestimate time passed during the early hours of sleep and underestimate during the later hours. Time estimation during dreaming are much more variable and some people claim to have dreamt a whole lifetime in one dream. However, the best experiments to test this come from those very rare people who can induce lucid dreams (knowing they are dreaming) at will, and then signal to experimenters to indicate what they are doing in the dream. When asked to count to 100 while dreaming or while awake, the times taken match closely. And when asked to estimate how long a dream event took, those estimates are accurate. So if time does go fast when you are asleep, you are unusual!

Why do little girls like pink ?

Probably because of social pressure. In Britain and the USA, older girls like pink more than boys do, but they could already have been influenced by expectations. So studies have tested one- to two-year-old's by using the ‘preferential looking task’, which measures what the children like to look at the most. The studies found that preference for toys differ by sex, with boys looking longer at cars and girls at dolls, but preference for color do not. So perhaps it’s not surprising that back in 1918 the trade publication Earnshaw’s Infants’ Department wrote that babies’ clothes should be pink for a boy and blue for a girl.

Why do we have moles on our skin?

During the first 12 weeks of pregnancy, the developing fetus is making melanocytes – the skin cells that produce ordinary skin color. These aren’t always evenly spread out: random areas will acquire a cluster and during your life, these clusters can grow into a mole.

Moles are quite different from freckles. Almost everyone has from 30 to 60 moles on their body, but freckles only occur in people with certain genes – particularly the one responsible for red hair. Freckles also need sunlight to trigger them, while moles appear spontaneously.

What makes people afraid of the dark?

Loss of vision. Sight is our strongest sense and some of our natural predators, such as the big cats, had better night vision than our ancestors did. Our ancestors also had to watch out for enemy raids; even today, we may justifiably fear being burgled.

But our greatest fears come from our own minds. Many children, and some adults, are terrified of the monster under the bed. This is called the ‘sense of presence’ and is often associated with sleep paralysis, when you wake up unable to move. These monsters are due to unusual activity in areas of the brain. Then there are all those ideas that we don’t like to face – our shame, guilt, anger, anxiety or whatever it may be. These seems far worse in the dark because our brains are deprived of the visual input that keeps them busy and suppresses those unwanted thoughts.

Why do bees die after stinging you?

Honey bee stings have a barbed ratchet mechanism that pulls the stinger into the initial wound. This didn’t evolve as a suicide mechanism – honey bees can pull their stings out after stinging other insects. It’s meant to drive the stinger in as deep as possible; it just happens that mammal skin is too fibrous to release the sting, so the abdomen is torn open when the bee tries to escape afterwards. Honey bees are the only species to suffer this fate, but the cost to the hive of losing some workers is worth it for an improved ability to repel honey thieves.