The Science of Being Human

But evolution is not a process of increasing complexity, nor any other measure of superiority you can find.

Our genus Homo contains just one species at the moment, and that’s us

none of us is an island and we all live out our lives surrounded by other humans.

and to my mind there is nothing more fascinating than the science of being human.

he system was invented back in 1735 by one of the great scientists of the eighteenth century, a Swedish naturalist called Carl Linnaeus

the humble and dull-looking lymphocytes turned out to be at the heart of the system. Not only that, there are three distinct flavours of lymphocyte: the B-cells make antibodies, the T-cells identify foreign agents in our bodies and the natural killer cells seek out and destroy our own cells that have become infected with viruses.

Most of these bacteria can be found in your intestines, but they are also all over your skin. The figure you see often quoted of 100 trillion bacteria inside a person has recently been downgraded somewhat to a mere 40 trillion bacteria, a number about 10 per cent greater than our body cell count. So, technically, if you consider the number of cells, you and I are more bacteria than we are Homo sapiens.

The human body is made up of some 37 trillion cells, which is an unfeasibly large number (see here for more on big numbers). For a long time, it has been known that there are at least the same number of bacteria living in you.

What has become apparent is that there is another source of control that is not strictly human – the bacteria living in you.

You and I have an extraordinary ability to know at any instant where the various bits of our body are with respect to all the other bits. This sense is known as proprioception, and is the most important of the senses that fall outside of the usual five we were all taught in school. You can think of proprioception as an internal sense rather than an external one. The traditional five senses – sight, hearing, taste, smell and touch – are all external senses in that they all feed information about the environment outside of our bodies to our brain. Proprioception is internal and gives us a knowledge of the state of what’s inside us.