Why do we have five fingers and five toes?
It’s probably nothing more than an accident. All tetrapods (the group of vertebrates that includes the mammals, birds, reptiles and amphibians) are descended from a pentadactyl ancestor. Pentadactyl means ‘five-fingered’ and this basic pattern has been preserved in all descendant animal groups. The common ancestor of the tetrapods was a lobe-finned fish living in the Devonian period, around 365 million years ago. The fossil record also shows fish with six and seven ‘fingers’ in their fins at around the same time, but there is no clear reason why the five-fingered form survived to become the template for land life. Possibly having fewer finger bones allowed each to become stronger and this helped when crawling out of the water. However, there is nothing magic about the number five and subsequent evolutionary pressures have driven many species to fuse fingers and toes together to form thicker, stronger hooves and claws that are better suited to their particular environment.
Why is my beer brown, but the head white?
The brown colour comes from malt, which is produced by allowing barley grains to germinate and then roasting them. A low roasting temperature makes a light beer. A higher temperature makes a darker beer. Just be thankful that you aren’t living in the 19th century, when some publicans tried to shortcut the process by adding concentrated sulfuric acid to their light-coloured beers, carbonising the sugars to produce an instant dark brown colour, and instant stomach problems in those who drank it. The bubbles in the head are surrounded by a film of liquid beer, but the film is so thin that it can’t absorb enough light to affect the colour of white light as it passes through. White light reflected from the surface of the bubbles also stays white, giving it its overall white effect.