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30.1 Evolution of Primates
The major groups of primate are listed.
The evolutionary tree shows the relationships of the primate groups.
Prosimians, monkeys, apes, and humans are included.
Most primate are adapted to live in trees.
The evolution of primate is characterized by a large and complex brain, a flattened face, and a reduced reproductive rate.
These are useful for living in trees.
The first group of primate may have looked similar to today's prosimians.
The New World monkeys and the Old World monkeys are the modern monkeys.
The apes can be divided into two groups, the Asian apes and the African apes.
Humans are also primate.
Chimpanzees have prehensile hands and feet, meaning they are adapted for grasping and holding.
Flat nails and sensitive pads on the undersides of fingers and toes have been used for grasping objects in most primate.
Old World monkeys, great apes, and humans have opposable thumbs.
A human's thumb is opposable.
The evolution of the primate limb was important for their life in trees.
Chimpanzees are able to grasp and release tree limbs with mobile limbs.
They allow primate to bring food to the mouth.
The snout and face of a primate are evolutionary trends.
The decline in smell and reliance on vision may be associated with these.
Most primate eyes are located in the front, where they can focus on the same object from different angles.
The snout and eyes of a primate are at the front of the head.
The result is a binocular field.
Page 564 is better for visual acuity because the retina contains cone cells and rod cells.
The blurry image is in shades of gray because rod cells are activated in dim light.
Cone cells need bright light, but the image is sharp and in color.
The fovea is a region of the retina where cone cells are concentrated.
The brain is more beneficial than sense organs.
The evolution of the primate's brain is larger and more complex.
The brains of prosimians, such as lemurs and tarsiers, are similar to those of apes and humans.
The portion of the brain devoted to smell is smaller in apes and humans, and the portion devoted to sight has increased in size and complexity.
The brain is more focused on controlling and processing information from the hands and thumbs.
Good hand-eye coordination can be achieved.
A reduction in the rate of reproduction is one of the trends in primate evolution.
It takes time for forebrain development.
It is difficult to care for several offspring in the trees while moving from limb to limb in a primate; one birth at a time is the norm.
There is an emphasis on learned behavior and complex social interactions in the juvenile period of dependency.
The evolution of primate during the Cenozoic era is shown in Figure 30.4.
The data shows that the hominins and gorillas are related and that they must have shared a common ancestor.
The hominines are now grouped together.
The primate is descended from a tree shrew.
The time when each type of primate deviated from the main line of descent is known from the fossil record.
For example, a common ancestor for hominines was present about 7 mya, for the hominoids about 15 mya, and for anthelms about 45 mya.
The hominines and orangutan are included.
The gibbon and hominids are part of the hominoids.
The hominoid common ancestor was the first to evolve.
The world monkeys lack prehensile tails and have protruding noses.
The rhesus monkey has been used extensively in medical research and is one of the better-known Old World monkeys.
New World monkeys, which have long, prehensile tails and flat noses, are found in parts of Mexico and Central America.
The first primate fossils were found in Africa.
Ancestors of New World monkeys arrived in South America around 40 mya.
The Atlantic crossing was so large that it is not certain how they arrived.
Chimpanzees, gorillas, and orangutans were classified into different families because of the difference in chromosomes number.
The study of transposons provided additional evidence.
Transposons are mobile elements in the genome.
There are many copies of transposons in the human genome, most of which are located in one location.
They are from the past.
Any similarity in transposon patterns between two species can be seen as evidence of a common ancestor.
Humans and Chimpanzees have the same patterns of transposons in their genomes.
This similarity suggests that the transposon was in this location before the split.
Nonfunctional copies of genes that were active in the past are pseudogenes.
Most pseudogenes are inactive due to the fact that they can't code.
The pattern of pseudogenes in humans is similar to that in Chimpanzees, but it varies from other great apes.
The reclassification of the primate most closely related to us has been caused by these and other studies.
All of the great apes are in the same family as humans.
The base sequence of humans and Chimpanzees is the same.
When we compare the two genomes, we find that many stretches of DNA are missing from one or the other.
We know that in the evolution of mammals there was an explosion in the amount of noncoding sequence compared to the number of coding genes.
Since their lines of descent separated, each mammal may have had a different amount of noncoding DNA.
The stretches of noncoding DNA that were retained by a particular primate may account for the differences.
The genes controlling the development of the brain may have been affected the most by the gaps in the human genome.
The larger size of our brains may be related to this.
2 is a fusion of two genes.
Africa and the Arabian Peninsula joined with Asia and the apes migrated into Europe and Asia.
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