Human Evolution: The Very Fact
Human evolution: The very fact that humans evolved from apes supports the theory of evolution and natural selection. There is some evidence to support the fact that humans are descendants of apes; notably, the fossil Australopithecus africanus resembles both humans and apes with a rounded brain, bipedalism, smaller teeth, and feet that resemble modern humans. The Australopithecus africanus could be the transition between apes and humans, which proves the theory of evolution. Also, humans are continuing to evolve today. One of our most recent evolutions is the evolution to drink cow’s milk. Humans have evolved a lactose-tolerant gene because of the selective pressure of drinking cow’s milk. People with the lactose intolerant gene have the older version of the gene.
Death and Aging: This is proof for evolution because death and aging are the driving forces of evolution and natural selection. If the parent generation does not die, the new generation will not be able to replace the old genes with a set of new mutated ones. This replacement of genes from generation to generation occurs with death of the previous generation, and can only happen with death. An example is the perennial prairie grasses that grow in the midwest and never die, because their roots remain intact. However, they are not able to evolve because they simply do not have room for a new generation. This shows that evolution does occur and death is the driving force.
Evolutionary psychology: Although evolutionary psychology is not an actual field of science, it does provide some evidence for evolution by suggesting that our modern behaviors are affected by evolutionary pressures. One example is the general trend of male promiscuity and female modesty. Evolutionary psychologists believe that this occurs because females generally had the burden of investing more energy in a child, so they did not want to have too many children and generally only had one partner. Males, on the other hand, have an evolutionary need to pass on their genes to as many offspring as possible. This proves the theory of evolution and natural selection because it acknowledges that we had pressures that helped us evolve our own unique behaviors.
Antibiotic resistance: This proves the theory of evolution and natural selection in bacteria. Antibiotics only became a selective pressure in the mid 1900’s, because that is when antibiotic resistance evolved. Basically, antibiotic resistance is the evolution of pathogenic bacteria to be resistant to antibiotics. The bacteria that acquired a mutation that allowed them to resist antibiotics survived, and were able to pass on their genes to the next generation of bacteria. The number of pathogenic bacteria increased through natural selection. This demonstrates the existence of evolution, but it is also a problem for humans who need to continue to develop new drugs to fight bacterial infections.
Eugenics: Eugenics is “artificial selection” but with people. Essentially, it aims to increase the “desirable” traits in people, such as intelligence, athleticism, and good looks, while decreasing the poor habits such as genetic diseases. While I do not support this at all, it does prove that selection plays a part in evolution. In this case, sexual selection attempts to evolve a new race of “super people” who have all of the desired characteristics of many people. After the Nazis began using eugenics by banning minorities from reproducing while encouraging Aryans to reproduce more, the idea became despicable. Although laws were soon put in place banning eugenics, it still shows the power of evolution. Also, people used natural selection as proof for eugenics, saying that only the “fittest”, most desirable humans should be allowed to pass on their genes, because that is exactly what happens in nature.
Neuroscience: Neuroscience is the study of the brain and the nervous system, and a large part of neuroscience is studying how signals travel through the body. Molecules play a very big part in sending messages back and forth between neurons – in fact, without molecules such as neurotransmitters and ions, we would not be able to send messages through the body. Neurotransmitters such as acetylcholine play a vital role in sending messages. They bridge the gap between two neurons and allow the message to transfer from the axons of the message sending neuron to the dendrites of a message receiving neuron. Also, in another form of signaling (electrical signaling), sodium, chlorine, and potassium ions flow from cell to cell. This shows just how much molecules affect us – we would not be able to survive without them!
Biology of love: I was honestly extremely surprised to learn that love is just a collection of different molecules and hormones that each have a different effect on the body. There are different molecules that are activated, depending on the type of love (such as mother to child love, child to mother love, instant attraction, mid term and long term love). For mother to child love, a series of hormones are triggered during childbirth, such as endorphins. The purpose of these endorphins is to help the brain associate childbirth with happiness instead of pain, so that women would not turn away from reproducing. Also, in lust or immediate attraction, hormones such as DHEA and testosterone are released. I find it amazing that something as intimate as love can be caused by several different molecules.
Immune system: The immune system contains several molecules that aid in the defense of the body. One example of such a molecule is an antibody, which is manufactured by B-cells. Antibodies travel through the blood and bind to different antigens, which are more molecules that can help them determine the existence of a pathogen. If they find a pathogen, they signal the 3rd line of defense. Another molecule is the Major Histocompatibility (MHC I) molecule which helps white blood cells identify cells of the body. Red blood cells are the only cells in the body which are not coated with MHC I, so any cells that do not have MHC I will be attacked. These are just two out of several molecules that play a vital role in the immune system and defending our body.
Venom and toxins: Venom and toxins themselves are simply just molecules that can have very negative effects on the body. They are usually produced by snakes, spiders, cone snails, jellyfish, and some bacteria. Some examples of molecules that are found in venoms include fasciculin, which freezes muscular movement by blocking the neurotransmitter acetylcholine. It causes the body to enter a state called tetany and also freezes the diaphragm, which causes suffocation. Another molecule, ricin, is produced in castor beans and destroys the ribosomes inside cells. Venom shows how molecules can affect cells and living organisms, but in a negative way.
Genetic diseases: Before addressing genetic diseases, we should keep in mind the fact that a majority of what defines our physical features and internal workings is written in one extremely complex molecule called DNA. This alone shows how much of our life is controlled by molecules that are not alive – without DNA, we would not be able to survive. Genetic diseases show how a small change in a molecule can affect us drastically. They are essentially changes in DNA that cause negative effects in the human body. This chapter shows how much molecules can affect us – we rely on them for basic, daily functions. If they become slightly changed, we are affected.
Introduced species: Introduced species are a very big problem in many parts of the world, and they all stem from a human cause. When people move animals from their native habitat to a new one, they are severely endangering the native species of the new habitat. The introduced species will no longer have its natural predators to keep the population in check, and it will be free to reproduce. It will also consume a lot of the native species’ diet, or hunt vulnerable native species such as birds. This has happened with the case of rabbits in Australia, who were introduced for human sport. However, they multiplied and caused severe consequences to the environment, such as threatening the native herbivores by devouring all of the plants. Even now, people are struggling to control the rabbit population. This shows how much humans have affected delicate ecosystems by introducing species to new habitats.
Genetically modified organisms: By genetically modifying organisms, humans are affecting the environment. GMOs have long been a controversial topic because of some of the harmful side effects. One of the consequences of growing GMOs is the effect on the environment. One example is Round-up Ready plants: because of the rise in Round-up Ready plants, farmers are using Round-up more often. This is killing some vital plants that are necessary for other animals, such as milkweed. Monarch butterflies need milkweed as a food source for their caterpillars, and the decrease in milkweed is affecting the monarch population. This shows that human created GMOs can affect the environment.
Synthetic biology: Synthetic biology shows how humans are beginning to alter individual genes and create new organisms. This proves that humans are altering our environment by changing one species at a time. Humans have already created a new species of bacteria, called Mycoplasma laboratorium, and are working to create new organisms that produce antibiotics or biofuels. This shows that humans have gone from altering the environment to altering individual genes. Such small changes have the potential to have a huge impact on our environment.
Bioremediation: Bioremediation is the use of microbes, plants, or fungi, to restore a polluted environment. This is used to clean up oil spills or other polluted areas that would be very difficult to clean. An example is when bacteria were used to clean up a jet oil spill in 1992. Bioremediation has become a very useful tool that humans can use to clean environments. This shows that humans can affect the environment in a good way by reversing any problems they might have created. It proves that human actions can and do affect the environment in beneficial ways.
Global warming: Global warming demonstrates one of the negative effects that humans can have on the environment. It is caused by an increase of carbon dioxide, which can be correlated to human activities such as deforestation, petroleum used in cars and motorcycles, fertilizers, and factories. It is also worsened by the melting polar icecaps (which are caused by global warming) and the rise in methane levels. Global warming in turn leads to climate change, which could be detrimental to crops and agriculture, and could be extremely harmful to ecosystems. Global warming is a perfect example of just how much humans can affect the planet. It also proves that because we caused this problem, we can fix it.