Certain nasal structures and spaces in anthropoids exhibit well-known attributes of other known vestiges, such as variability in form or number. The cupular recess a vestige of the olfactory recess and some rudimentary ethmoturbinals constitute reduced structures that presumably were fully functional in our ancestors. Humans and at least some apes retain a vestige that is bereft of chemosensory function while in catarrhine monkeys it is completely absent. However, the function of the vomeronasal system also includes prenatal roles, which may be common to most or all mammals.
Notably, neurons migrate to the brain along vomeronasal and terminal nerve axons during embryogenesis. Fortunately, given that the climate fluctuated in Africa around the time that true humans first appeared, making good air conditioning vital, other parts of the human airways changed too. This may have made up for any inefficiency in the nose and nasal cavity, allowing humans to fully condition the air they inhaled.
In particular, the pharyngeal region of the throat — which is much longer in humans than in other primates — may have begun to lengthen at this time. Our long pharynx is often linked to our ability to talk , but Nishimura says that it also plays an important role in conditioning inhaled air.
Narrow nostrils, the thinking goes, create more turbulence in the inhaled air, which increases the level of heat and moisture exchange between the air and the tissue covering the wall of the nasal cavity. The Neanderthals are an apparently glaring exception to this rule — they lived in cold Europe yet had large wide noses.
But Rae and his colleagues have argued that this might be because Neanderthals actually evolved and adapted in relatively warm and humid conditions before later moving into Europe. Lemurs are an exception. They are very much like the early primates 50 million years ago. Note the marked difference between lemur, monkey, and human noses in the photos below. Most monkeys and apes have evolved relatively small noses like us, while lemurs have retained long snouts similar to foxes and raccoons.
It is not surprising that lemurs have a comparatively good sense of smell. Most mammals have about the same number of genes that code for odor receptors in their nasal tracks. However, the majority of these genes in humans, and presumably other large primates, are no longer functional. Recent research has shown that of the approximately 1, human olfactory receptor genes, only remain functional.
The rest have mutations that deactivate them. Does this really mean that people have a poor sense of smell? The answer is both yes and no. We are poor at sensing short-chain chemical compounds but good at discriminating between complex long-chain ones such as those of many foods and flowers. Dogs are just the opposite in this. However, the smelling ability of dogs is far superior to people in one way. Fewer molecules of a substance are usually needed for dogs to detect it. As the primate nose progressively shrank in size over millions of years, there was a corresponding increase in visual capabilities.
Many primates have color vision comparable to our own. All have binocular vision with fields of view that significantly overlap, resulting in true three dimensional 3-D depth perception or stereoscopic vision. At the same time, the field of view for peripheral vision was reduced. It is only in this field that we have stereoscopic vision. Monkeys and apes have about the same depth perception ability as humans, but the eyes of lemurs are farther apart resulting in a smaller overlapping field of view.
Additional information about primate color vision Depth perception is an invaluable tool for animals that need to move quickly. It allows them to judge the distances to important objects in their environment. For monkeys jumping from branch to branch high up in the canopies of forests, this is a matter of life and death.
Likewise, accurate depth perception is a critical capability for hunters, such as cats and hawks, who need to accurately judge distances in the pursuit of their prey. In contrast, it is often preferable to have greater peripheral vision if you are the prey. Compared to most other animals, primate brains are large relative to their body size. Those areas of the brain that are involved with controlling manual dexterity , eye-hand coordination, and stereoscopic vision have particularly expanded.
These traits were probably selected by nature mostly due to their usefulness in traveling in trees , manipulating objects, and getting food. The more capable uterus and placenta of primates support long gestation periods , or pregnancies, for animals of their size. For example, the mouse lemur has a gestation period of 60 days, but it is only 20 days for a comparable size rodent mouse.
M acaques, which are one of the most common groups of monkey species in the Old World, have Among comparable size domesticated dogs, it is only about 9 weeks. The result of long gestations is that offspring are born more mature and, therefore, have a greater chance of survival.
Primate mothers also are generally very protective and nurturing with their young. Subsequently, primates do not need to have many offspring to maintain their population numbers. Multiple births at any one time are rare for them. The time gap between generations is surprisingly long for the larger primates. Among humans today, parents are on average 29 years older than their children. By comparison, chimpanzee mothers are on average 25 years older than their offspring.
Among female gorillas, it is There frequently is a correlation between body size and longevity in the animal kingdom. Species with larger bodies generally live longer. However, p rimates have unusually long natural life spans for their size. For instance, mouse lemurs live about 8 years. Rodent mice rarely reach 2 years. Rats, which are slightly larger than mouse lemurs, can live 3 years.
Big monkeys, such as baboons, live up to 30 years. Male baboons can weigh as much as 90 pounds. Comparable size domesticated dogs have a life expectancy of only years.
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