|Amount of information available to different species|
Among all living species, there is a special one: ours. This has been said since antiquity, and has only been questioned in the last half century. Many biologists argue that the human species is one among many, that it cannot be considered superior to any of the others, either bacteria, insects, or other mammals.
There is, however, a quantitative and perfectly objective criterion that makes it possible to prove that the human species is unique, completely different from all others: the amount of information that each individual can handle.
For unicellular beings, the only information available to each individual is their own genome, which is easy to quantify: their bit value is approximately equal to twice the number of nucleotides in their genome. For viruses, from 10 to 50 kbits; for bacteria, up to 10 Mbits; for a unicellular eukaryote, up to 25 Mbits.
If we move to multicellular animals and plants, the size of the genome increases, and with it the amount of information it contains: about 200 Mbits for a nematode, up to several Gbits for vertebrates. For man it is estimated at about 6 Gbits, not much larger than the genomes of other mammals. In fact, the living being with the largest genome happens to be a fish.
In addition to the genome, vertebrates have a second source of information: their nervous system, especially the brain. The total amount of information contained in a brain is estimated at about 10 kbits for amphibians, 10 Gbits for reptiles, 200 Gbits for mammals.
Here man is unique: in proportion to the human body, our brain is larger than that of any other living species and is capable of storing no less than 10 Tbits (10 trillion bits), 50 times more than most mammals and a thousand times more than our own genome. It can be said that, with man, life crossed a critical point. For the first time in history, a single individual is able to reach such levels of information handling.
Five thousand years ago, with the invention of writing, man crossed a new critical point, a consequence of the previous one. We have become the only species with a third source of information, a memory external to our body. With the arrival of computers and Internet, this information has been made available to everybody and is still growing. Currently it is estimated that it has exceeded 100 exabits (100 quintillion bits, or 1020 bits: one followed by twenty zeros). Every human being, apart from what is contained in the brain, has access to extra information ten million times greater, as if we were connected with ten million brains apart from ours.
The attached figure summarizes this and combines (on a logarithmic scale) all sources of information available at any time for the species capable of handling most information, depending on the time elapsed from the origin of life to the apparition of the said species, in billions of years.