This list was found on the net and was originally drafted by Jocelyn Selim.
A tiny pit on each side of the septum is lined with nonfunctioning chemoreceptors. They may be all that remains of a once extensive pheromone-detecting ability.
EXTRINSIC EAR MUSCLES
This trio of muscles most likely made it possible for prehominids to move their ears independently of their heads, as rabbits and dogs do. We still have them, which is why most people can learn to wiggle their ears.
Early humans had to chew a lot of plants to get enough calories to survive, making another row of molars helpful. Only about 5 percent of the population has a healthy set of these third molars.
A set of cervical ribs—possibly leftovers from the age of reptiles—still appear in less than 1 percent of the population. They often cause nerve and artery problems.
A common ancestor of birds and mammals may have had a membrane for protecting the eye and sweeping out debris. Humans retain only a tiny fold in the inner corner of the eye.
A small folded point of skin toward the top of each ear is occasionally found in modern humans. It may be a remnant of a larger shape that helped focus distant sounds.
This small muscle stretching under the shoulder from the first rib to the collarbone would be useful if humans still walked on all fours. Some people have one, some have none, and a few have two.
This long, narrow muscle runs from the elbow to the wrist and is missing in 11 percent of modern humans. It may once have been important for hanging and climbing. Surgeons harvest it for reconstructive surgery.
Lactiferous ducts form well before testosterone causes sex differentiation in a fetus. Men have mammary tissue that can be stimulated to produce milk.
Bundles of smooth muscle fibers allow animals to puff up their fur for insulation or to intimidate others. Humans retain this ability (goose bumps are the indicator) but have obviously lost most of the fur.
This narrow, muscular tube attached to the large intestine served as a special area to digest cellulose when the human diet consisted more of plant matter than animal protein. It also produces some white blood cells. Annually, more than 300,000 Americans have an appendectomy.
Brows help keep sweat from the eyes, and male facial hair may play a role in sexual selection, but apparently most of the hair left on the human body serves no function.
Often mistaken for a nerve by freshman medical students, the muscle was useful to other primates for grasping with their feet. It has disappeared altogether in 9 percent of the population.
Our closest cousins, chimpanzees and gorillas, have an extra set of ribs. Most of us have 12, but 8 percent of adults have the extras.
A remnant of an undeveloped female reproductive organ hangs off the male prostate gland.
Lesser apes use all their toes for grasping or clinging to branches. Humans need mainly the big toe for balance while walking upright.
FEMALE VAS DEFERENS
What might become sperm ducts in males become the epoophoron in females, a cluster of useless dead-end tubules near the ovaries.
More than 20 percent of us lack this tiny, triangular pouchlike muscle that attaches to the pubic bone. It may be a relic from pouched marsupials.
These fused vertebrae are all that’s left of the tail that most mammals still use for balance and communication. Our hominid ancestors lost the need for a tail before they began walking upright.
The nasal sinuses of our early ancestors may have been lined with odor receptors that gave a heightened sense of smell, which aided survival. No one knows why we retain these perhaps troublesome mucus-lined cavities, except to make the head lighter and to warm and moisten the air we breathe.
In 1859, Charles Darwin (1809-1882) published The Origin of Species, which articulated the first full-fledged theory of evolution by natural selection. Darwin viewed the history of life like a tree, each fork in the tree’s limbs representing a shared ancestry. The tips of the limbs represented modern species and the branches represented the common ancestors shared amongst species. To explain these relationships, Darwin contended that all living things were related and descended from a few forms, or even from a single common ancestor, in a process he described as “descent with modification”.
Darwin’s view was controversial because humans did not receive special consideration in this evolutionary tree: they were merely one of its many branches. Though he did not make this explicit at first, his friend and supporter T. H. Huxley soon presented evidence that humans and apes shared a common ancestor. The popular press of the day misinterpreted this as an assertion that humans were descended from monkeys.
Darwin’s explanation of the mechanism of evolution relied on his theory of natural selection, a theory developed from the following observations:
1. If all the individuals of a species reproduced successfully, the population of that species would increase exponentially.
2. Except for seasonal fluctuations, populations tend to remain stable in size.
3. Environmental resources are limited.
4. The traits found in a population vary extensively. No two individuals in a given species are exactly alike.
5. Many of the variations found in a population can be passed on to offspring.
From these observations, Darwin deduced that the production of more offspring than the environment can support leads to a struggle for existence, with only a small percentage of individuals surviving in each generation. He noted that the chance for surviving this struggle is not random, but depends on how well-adapted each individual is to its environment. Well-adapted, or “fit” individuals will more likely leave a greater number of offspring than their less well-adapted competitors. Darwin concluded that the unequal ability of individuals to survive and reproduce leads to gradual changes in the population as the traits which help the organism survive and reproduce accumulate over generations and those that inhibit its survival and reproduction are lost. Darwin used the term natural selection to describe this process.
The variations in a population arise by chance mutations in DNA, but natural selection is not a process of chance: the environment determines the probability of reproductive success. The end products of natural selection are organisms that are adapted to their present environments.
Natural selection does not involve progress towards an ultimate goal. Evolution does not necessarily strive for more advanced, more intelligent, or more sophisticated life forms. For example, fleas (wingless parasites) are descended from a winged, ancestral scorpionfly, and snakes are lizards that no longer require limbs. Organisms are merely the outcome of variations that succeed or fail, dependent upon the environmental conditions at the time. In reality, when the environment changes, most species fail to adapt and become extinct.