Viviane Callier writes:

Our human brains can seem like a crowning achievement of evolution, but the roots of that achievement run deep: The modern brain arose from hundreds of millions of years of incremental advances in complexity. Evolutionary biologists have traced that progress back through the branch of the animal family tree that includes all creatures with central nervous systems, the bilaterians, but it is clear that fundamental elements of the nervous system existed much earlier.

How much earlier has now been made dramatically clear by a recent discovery by a team of researchers at the University of Exeter in the United Kingdom. They found that the chemical precursors of two important neurotransmitters, or signaling molecules used in nervous systems, appear in all the major animal groups that preceded creatures with central nervous systems.

The big surprise, however, is that these molecules are also present in single-celled relatives of animals, called choanoflagellates. This finding shows that animal neuropeptides originated before the evolution of even the very first animals.

The discovery “solves a long-standing question about when and how animal neuropeptides evolved,” said Pawel Burkhardt, who studies the evolutionary origin of neurons at the Sars International Center for Marine Molecular Biology in Norway. It also indicates that at least some of the signaling molecules fundamental to the operation of our brains first evolved for an entirely different purpose in organisms that consisted of only a single cell. [Continue reading…]