Last week’s World Science Festival event, “Planet of the Humans: the Leap to the Top,” opened with a contemporary dancer and a small, three-foot robot sharing the stage in a dance duet. The robot, which stood on its own two feet, “learned” as it went, with the dancer lifting its arms and giving it direction, support, and “love,” in the form of reassuring head nods and slight touches to keep it steady. Its progression was impressively quick, and soon enough it was mimicking the human dancer’s every move, from splits to rolls and beyond. The dance was an excerpt from choreographer Blanca Li’s “ROBOT,” an avant-garde performance currently at the Brooklyn Academy of Music. Continue reading
In December 2009, Cerebrum played online host to quite a debate: Does evolution explain why the human brain supports religious belief?
Dimitrios Kapogiannis and Jordan Grafman, scientists at the National Institutes of Health, argued that brain networks that evolved for other purposes have given rise to our capacity for religious belief and experience. Andrew Newberg, the radiologist and psychiatrist who wrote How God Changes Your Brain, argued that the brain may be an instrument of religious experience but is not necessarily the origin of that experience. Each side of the debate first wrote a position statement; they then exchanged statements and wrote rejoinders.
99.99 percent of species don’t have a brain like we have.
But as Dr. Rob DeSalle, curator in the American Museum of Natural History’s division of invertebrate zoology, explained at an event at the museum last night, studying organisms without brains is one of the best ways to study the human brain.
DeSalle moved through the Tree of Life—a diagram of species and their connections to one another—to describe how the brain and brain-like structures evolved.
Bacteria, for example, use chemicals to respond to the presence of other single-celled bacteria. They in effect act as a multicellular unit through this communication—and they don’t have a brain or a nervous system.
Social slime molds—or dictyostelium—take this ability one step further. They live in soil as single-celled, amoeba-like organisms. But they group together when faced with starvation or other adverse conditions, forming worm-like creatures capable of locomotion. Even without brains, slime molds make decisions. One species of slime mold, physarum, is known for its ability to efficiently find the quickest way through a maze. In addition, researchers have shown that dichtyostelium can carry the same mitochondrial mutations known to wreak havoc in the human nervous system.
Sponges have half of the genes required for synapses. And jellyfish, coral, and others members of the phylum cnidaria have neural nets—a series of cells that communicate through basic synapses. While not having a true brain, nematodes have a nervous system that forms a ring around their digestive system, a ganglia (a group of nerve cells), and the ability to make decisions based on smell.
Once we get to fish and lizards, the brain as we know it begins to take shape. These animals have a basic cortex, cerebellum, and basal ganglia. In mammals, an organizational change took place, with genes expressed in higher amounts, altering the size of certain brain structures.
As DeSalle described, human brains are most likely the result of genetic drift (chance changes in the gene pool of a small population), natural selection, and, mostly, luck. “Our brains are an inelegant solution to a problem,” concluded DeSalle. “They are part of an evolutionary heritage.”