sends a sound through the oil (which âfocusesâ the sound) and out to objects in the water. The sound bounces back to the dolphin and his brain forms a sound picture of whatâs out there. Humans canât use sonar because humans donât have any of the necessary sense structures.
Humans also have sensory receptors animals donât, like the huge number of cones in our retina for seeing color.
Iâve been talking mostly about vision, but all the other senses are different in different animals, too. Thereâs some fascinating new research about the relationship between vision and smell in New World versus Old World primates. Old World primates are the famous ones everyone knows about: gorillas, chimpanzees, baboons, orangutans, macaques, humans. New World primates are the smaller animals we call monkeys. New World primates usually live in trees in Central and South America; they have long prehensile tails and flat noses. Tamarins, squirrel monkeys, sakis, and marmosets are all New World monkeys.
Old World primates, like baboons, chimpanzees, and macaques, have trichromatic, three-color vision, but most of the New World monkeys (spider monkeys, marmosets, capuchins) only have dichromatic, two-color vision. (Some New World females have trichromatic vision, but not all.)
Whatâs interesting about this is that Old World primates and humans also have very poor ability to smell pheromones, which are chemical signals animals emit as a form of communication. (Most people think of pheromones as sexual signals, like the pheromones a female in heat emits, but a pheromone is any chemical used for communication. Ants, for instance, leave trails of scents behind them for other ants to follow.) About a year ago researchers found that Old World primates and humans both have so many mutations in a gene called TRP2, which is part of the pheromone signaling pathway, that itâs not working anymore. In the course of evolution, the pheromone system in Old World primates, including humans, broke down.
It turns out that when we gained three-color vision we probably lost pheromone signaling. Jianzhi George Zhang, an evolutionary biologist at the University of Michigan, ran a computer simulation to find out when the TRP2 gene started to deteriorate, and discovered that TRP2 went into decline at the same time Old World primates were developing trichromatic color vision, around 23 million years ago. 12
Probably what happened was that once Old World primates could see in three colors they started using their vision to find a mate, instead of their sense of smell. That theory fits with the fact that a lot of Old World primate females have bright red sexual swellings when theyâre fertile, while New World monkeys do not. Once monkeys no longer needed a good sense of smell to reproduce successfully, their ability to smell probably went into decline as a direct result.
That would have happened because use it or lose it is a principle in evolution. If monkeys with a poor sense of smell can reproduce just as well as monkeys with an excellent sense of smell, the monkeys with the poor ability pass all of their weak or defective smell genes on to their offspring, and any spontaneous new mutations in the smell genes donât get winnowed out. It looks like thatâs what happened to Old World primates. The normal mutations that happen in the process of reproduction just kept accumulating until no primates had a working copy of TRP2 anymore. Improved vision came at a cost to their sense of smell.
S AME B RAIN C ELLS , D IFFERENT P ROCESSING
So far Iâve been talking about the sense organ or sense receptor part of animal perception: animals have different sensory organs than wedo, organs that let them see, hear, and smell things we canât. But the other half of the story is where things get interesting, and that is the differences in brain processing.
All sensory data, in any creature, has to be processed by
Humans also have sensory receptors animals donât, like the huge number of cones in our retina for seeing color.
Iâve been talking mostly about vision, but all the other senses are different in different animals, too. Thereâs some fascinating new research about the relationship between vision and smell in New World versus Old World primates. Old World primates are the famous ones everyone knows about: gorillas, chimpanzees, baboons, orangutans, macaques, humans. New World primates are the smaller animals we call monkeys. New World primates usually live in trees in Central and South America; they have long prehensile tails and flat noses. Tamarins, squirrel monkeys, sakis, and marmosets are all New World monkeys.
Old World primates, like baboons, chimpanzees, and macaques, have trichromatic, three-color vision, but most of the New World monkeys (spider monkeys, marmosets, capuchins) only have dichromatic, two-color vision. (Some New World females have trichromatic vision, but not all.)
Whatâs interesting about this is that Old World primates and humans also have very poor ability to smell pheromones, which are chemical signals animals emit as a form of communication. (Most people think of pheromones as sexual signals, like the pheromones a female in heat emits, but a pheromone is any chemical used for communication. Ants, for instance, leave trails of scents behind them for other ants to follow.) About a year ago researchers found that Old World primates and humans both have so many mutations in a gene called TRP2, which is part of the pheromone signaling pathway, that itâs not working anymore. In the course of evolution, the pheromone system in Old World primates, including humans, broke down.
It turns out that when we gained three-color vision we probably lost pheromone signaling. Jianzhi George Zhang, an evolutionary biologist at the University of Michigan, ran a computer simulation to find out when the TRP2 gene started to deteriorate, and discovered that TRP2 went into decline at the same time Old World primates were developing trichromatic color vision, around 23 million years ago. 12
Probably what happened was that once Old World primates could see in three colors they started using their vision to find a mate, instead of their sense of smell. That theory fits with the fact that a lot of Old World primate females have bright red sexual swellings when theyâre fertile, while New World monkeys do not. Once monkeys no longer needed a good sense of smell to reproduce successfully, their ability to smell probably went into decline as a direct result.
That would have happened because use it or lose it is a principle in evolution. If monkeys with a poor sense of smell can reproduce just as well as monkeys with an excellent sense of smell, the monkeys with the poor ability pass all of their weak or defective smell genes on to their offspring, and any spontaneous new mutations in the smell genes donât get winnowed out. It looks like thatâs what happened to Old World primates. The normal mutations that happen in the process of reproduction just kept accumulating until no primates had a working copy of TRP2 anymore. Improved vision came at a cost to their sense of smell.
S AME B RAIN C ELLS , D IFFERENT P ROCESSING
So far Iâve been talking about the sense organ or sense receptor part of animal perception: animals have different sensory organs than wedo, organs that let them see, hear, and smell things we canât. But the other half of the story is where things get interesting, and that is the differences in brain processing.
All sensory data, in any creature, has to be processed by
Similar Books
