Were there certain conditions that acted as evolutionary pressures, ultimately influencing how the synapses developed?
The principal driving force behind the doubling of proteins at different evolutionary boundaries was the changes in the structure of the genome. Genome duplication events led to the doubling of many genes. That was a major driving force behind the expansion of gene numbers. Although the genome duplications provided more genes for the animals to utilise, we found that there were certain proteins that were preferentially used by the synapses of invertebrates and vertebrates. These were the type of proteins that are on the surface of the cells, such as neurotransmitter receptors. The second type of complexity – a fascinating puzzle – emerged as a result our study. We were interested in the vertebrate nervous system – mammalian, in particular – and we calculated that these complex synapses arose hundreds of millions of years before the anatomically big mammalian brains. We wondered whether there was some connection. Was having more synapse proteins a prerequisite to the subsequent growth a
