The Opposable Thumb
One of the miracles of evolution is hand dexterity. And the important part of hand performance is the ability, length, and strength of the thumb. In a war, Julius Caesar cut the thumbs of captured soldiers so they couldn’t hold weapons anymore. You cannot practically do much without a thumb opposing the other fingers. In the opposition, the strong, relative shorter thumb faces the other fingers and makes a strong grip. Thumb opposition appeared around 2.6 million years ago. It first was used to help climb trees or make simple tools. As brains continued to develop and the demand for complicated performance grew, the importance of thumb opposition also increased. The thumb is not just a simple stick facing the other fingers, it needs the complex cooperation of the ordering brain, the complex carpo-metacarpal joint, strong thenar muscles, and the proficient median nerve in coordination with the other parts of the hand.
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Walking Upright
Standing upright is a privilege for human beings. Becoming bipedal rather than going on four feet was helpful for the homo species in different aspects. By standing on two feet, the two other limbs were free to use for other jobs such as handling tools. By the gradual change in the environment and habitats, these living things came down the trees and standing and walking upright helped them have a better view of their surroundings. Measurements show that walking on two feet is more efficient and consumes much less energy. This helped homo species to preserve energy and help their brains continue to grow. Despite all these good changes, walking on two feet may have had some downsides as well. The spine's shape and curvature has changed to help humans stand and walk upright. Some assume that this change in the spine's curvature may explain the cause of neck and low back pain in human beings.
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Brain Size
As species stepped up the ladder of the evolution tree, their brains gradually enlarged, increasing the performance capacity and more adaptability to the environment. Is it true that a larger brain always has a better performance? The adult human brain weighs on average about 1.5 kg (around 3 lb.) with a volume of 1400 cm3. The size and volume of brains had been increasing from the most primitive species to Homo sapiens, but there was an exception: Neanderthals. Neanderthals had a brain volume of 1680 cm3. Does this mean that Neanderthals were more intelligent or had more cognitive abilities than homo sapiens? Another important point is that although Homo sapiens are on a daily endeavor of pushing the horizons of intelligence and cognition, the average brain volume of Homo sapiens has been decreasing by 10 percent in the past 40,000 years. It is like making thinner and lighter smart phones and laptops with much more capabilities.
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Why Don't We Walk Right After Birth?
Have you seen when a mammal gives birth to a baby and the offspring begins to stand moments after dropping from its mother's belly? And after a few hours it starts to walk, following its mother... Why does this not happen in human babies? It takes more than a year or so, for a human baby to start standing and walking. It is said that it takes two years for a human offspring to acquire the motor abilities and strength of a newborn mammal. This is attributed to the human brain size. A baby human's brain is bigger in comparison to other animal's and its passage through the birth canal is more difficult; so evolution has managed some of the brain maturation that happens in other animals during their embryonic period, to be done during the months after birth in human beings.
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The Different Eyes
When you study the eye anatomy, you will notice an interesting point. As you know, light enters the pupils, passes the lens and other transparent structures inside the eye, and reaches the retina. The light sensitive cells (rods and cones) are on the retina. These cells produce electric impulses and transfer them, through nerve fibers, to the brain. But the interesting point is that rods and cones lie deeper on the retina and the light has to pass some other cells (bipolar and ganglion cells) to reach them. This is called backward retina. Don't you think this decreases the efficacy? Yes it does! There is another kind of eye in nature that has evolved independently; the eyes in cephalopods like octopus. In cephalopods the retina is front facing and the entering light first reaches the photoreceptors (rods and cones) and scientists have seen that these other kinds of eyes are more efficient and have no blind spots.
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Wisdom Teeth
We and apes are both primates but there is a significant difference between the shape of our faces and heads. Can you guess what? During the past million years, our ancestor's brain continued to grow and as result, the head became bigger and bigger. To compensate, the face parts including the brow, jaw, and cheeks got smaller. This is why there is not enough space for the wisdom teeth in our mouths. Wisdom teeth are usually a source of problem and many let their dentist remove them. Do you know there are some people without wisdom teeth? I am one of those!
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Many believe that we, the humans, are the best possible creatures on earth. Today we know that might not be true. Many animals, each have specific abilities far more sophisticated and, according to Charles Darwin, much more adaptable to the surrounding environment. On the other hand, there are some body part in us that might be of no use anymore. they may even be a source of inconvenience: for example, the wisdom teeth mentioned above. In addition to that, other example include coccyx or tailbone, appendix, erector pili which causes goosebumps in the cold, a tendon in wrist called Palmaris Longus, and some ear muscles causing our ear to wiggle. Fun fact, Stan Laurel, the vintage comic actor, used his ear wiggling ability to amuse the audience and gain more popularity.
Ernst Mayr
Mayr was a great Evolutionist. Some believe him to be one of the most prominent figures in this field after Charles Darwin. He once commented that it's possible to explain everything in nature with the two main laws of natural selection: to survive and to reproduce. The former says that every single creature endeavors to survive. This includes itself and the group it identifies with, the family or the tribe. He believes even feelings such as hate and love, and human behaviors such as decision makings and policies can be explained under these two main laws. He once mentioned that he had encountered an exception that he could not explain with natural selection: Altruism.
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Ernst Mayr
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Milk Tolerance
Milk is an important part of the daily diet in many families and a great source of calcium, not only in children but also in adults. It may be difficult to imagine that tolerance to milk has been a part of evolutionary process in human. This can be more understandable if you consider that other mammals normally lose the ability to digest lactose after they stop drinking their mother's milk. Lactase persistence and the ability to digest milk is a new evolutionary change and only in some human population. There are some speculation around the reason why lactose tolerance has appeared in some and not in others. One explanation is that milk supplied vitamin D and calcium. Due to this hypothesis, in areas of sunlight scarcity, milk tolerance has evolved to provide calcium in the body. Maybe that is why people are more milk tolerant in areas of low sunlight in northern Europe.
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How Do Diseases Not Disappear With Natural Selection?
Since natural selection, according to Charles Darwin, is supposed to help creatures survive and reproduce, it is rational to assume those mutations and maladies that worsen wellbeing and contradict survival and reproduction are doomed and gradually are to disappear as evolution continues. So why haven't diseases disappeared with natural selection? the answer is that some diseases only appear after the age of reproduction. These Diseases, such as Alzheimer, although debilitating and gruesome, cannot interfere with the process of natural selection because they appear only when the patient is no longer able to conceive. All his/her offspring are already born with their indisposed mutant genes.
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