The gap area where nerve cells connect to each other is called the synapse. Our higher intelligence comes not just from more synapses connecting between more nerves. The structure of each synapse is far more complex in creatures with higher intelligence.
Current thinking suggests that the protein components of nerve connections - called synapses - are similar in most animals from humble worms to humans and that it is increase in the number of synapses in larger animals that allows more sophisticated thought.
"Our simple view that 'more nerves' is sufficient to explain 'more brain power' is simply not supported by our study," explained Professor Seth Grant, Head of the Genes to Cognition Programme at the Wellcome Trust Sanger Institute and leader of the project. "Although many studies have looked at the number of neurons, none has looked at the molecular composition of neuron connections. We found dramatic differences in the numbers of proteins in the neuron connections between different species".
"We studied around 600 proteins that are found in mammalian synapses and were surprised to find that only 50 percent of these are also found in invertebrate synapses, and about 25 percent are in single-cell animals, which obviously don't have a brain."
It would be interesting to know for these 600 proteins whether there are differences in their genes between humans. The differences might account for some genetically caused differences in intelligence and personality.
Synapses used to be taught in neurobiology classes as pretty simple places where synaptic endings of axons release neurotransmitters that float across to bind to receptors on dendrites. Then that binding causes a wave of depolarization which propagates along a nerve. Well, the synapses probably function in much more complex ways.
Synapses are the junctions between nerves where electrical signals from one cell are transferred through a series of biochemical switches to the next. However, synapses are not simply soldered joints, but mini-processors that give the nervous systems the property of learning and memory.
Some day the ways in which memories get stored and information gets processed will be understood in enormous detail. Will that cause more people to abandon belief in a soul?
"The molecular evolution of the synapse is like the evolution of computer chips - the increasing complexity has given them more power and those animals with the most powerful chips can do the most," continues Professor Grant.
Simple invertebrate species have a set of simple forms of learning powered by molecularly simple synapses, and the complex mammalian species show a wider range of types of learning powered by molecularly very complex synapses.
"It is amazing how a process of Darwinian evolution by tinkering and improvement has generated, from a collection of sensory proteins in yeast, the complex synapse of mammals associated with learning and cognition," said Dr Richard Emes, Lecturer in Bioinformatics at Keele University, and joint first author on the paper.
What I want to know: Do other species have advances in their synaptic structure that humans do not have? In particular, some bird species are very smart for the size of their brains. Do they have very sophisticated synaptic structures that would allow them to be as smart or even smarter than us if only their brains were as large?
|Share |||Randall Parker, 2008 June 21 08:43 PM Brain Evolution|