Have we stopped evolving?
Everyone who is alive today descended from one woman who lived in East Africa about 200,000 years ago. The researchers call her Eve, and her genetic material is still found in all our cells. In Eve’s time there were very few people, and only her descendants remain today. Little by little they have spread across the globe. Even though we have spread across the world, our genetic material is surprisingly similar. There are no clear genetic differences between people from different continents or different ethnic groups. There are actually much greater differences between different chimpanzees. Since we are so similar, some people wonder whether we have actually stopped evolving.
Menneskets evolusjon med et menneske med smarttelefon
Some traits are favoured
For evolution to take place, more individuals must be born than those who survive.The individuals must be different, and those differences must be hereditary. The hereditary traits are passed from parent to child. Some traits are better adapted to the environment than others. Individuals with these traits have a greater chance of growing up and having children themselves, and these traits are then passed on to the next generation.
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New traits
New traits enter the population in three different ways.
Mutation
When we make reproductive cells that turn into children, our genetic material is copied, and the child receives a mixture of maternal and paternal genes. However, when genetic material is copied, small errors can sometimes creep in, and these errors are called mutations. Some such mutations go unnoticed, and some can result in new beneficial traits while others result in negative traits.
Gene flow
New traits can also enter a population with genetic material from other ethnic groups. If two groups of people live separately for many years, they will develop differently. If these groups come back together and share genetic material, new combinations of hereditary characteristics are formed. This is called gene flow.
Reproduction
A baby receives genetic material from their biological parents, and this is how combinations of genes are put together. The human species is relatively young. We reproduce slowly compared to many other animals, and there are limits to how many new traits will arise in the population in a few hundred thousand years. Your genetic material differs only 0.1 percent from mine. Even though we look different, the entire human race has close genetic ties.
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Environment and natural selection
Heredity and biology are not the only factors that contribute to our development. The environment also plays an enormous role. For new traits to be inherited, they must increase our chances of survival. If an individual has traits that enable them to survive better and have more children than others, this individual’s genes stand a better chance of being passed on to the next generation.
Naturalist Charles Darwin called it natural selection or «survival of the fittest». This means that it is important to have traits that enable you to make the best possible use of your surroundings. When the environment changes, other genes may become more useful in the new environment. The best adapted is the one who will manage the best. This is where human development gets complicated. Through culture, science and technology, we are constantly changing our surroundings, and thus we influence nature and the role of biology.
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Charles Darwin illustrasjon
From Eve to Lucy
Our human-like ancestors were completely at the mercy of the environment they lived in. Consider Lucy, the fossil Australopithecus afarensis woman who lived 3.2 million years ago. She had ape-like features, including a large jaw, long arms and fur, but she walked on two legs. She lived in the trees, but the environment was changing – the trees were disappearing, and Lucy was spending more time on the ground. Eggs found near her indicated she was hoarding food.
Between Lucy and Eve, our ancestors were forced out of the forests and onto the plains by climate change. They had to walk under the scorching sun to survive, and body hair became a nuisance. Bare skin and the ability to sweat to get rid of body heat became an advantage. Environmental pressure forced our ancestors’ genes to change.
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Ape, Lucy
The brain develops
Through reproduction, mutation and gene flow, humans eventually developed larger brains, smaller jaws and more advanced social groups. We tamed fire and invented tools, and as we became more intelligent, we changed our environment more and more. This changed everything. When agriculture emerged around 10,000 years ago, our history changed drastically and with it, our genes changed as well. Suddenly we had the ability to produce our own food, close to where we lived.
Changes to the human body
Researchers at Harvard University in the US have examined genes from 230 people that lived between 8,500 and 2,300 years ago, and have discovered several exciting differences in body height, metabolism and skin colour.
For example, about 4,000 years ago, a mutation appeared that meant that adult humans could digest milk. Fair skin became more common, which may have been due to people eating more plants and getting less Vitamin D. The immune system also changed, so that it has become possible for people to live more closely together.
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Neandertalere i et grønt og frodig landskap
Knowledge and culture change our surroundings
In humans, it is not just the genes that are inherited. We also pass on our culture to our descendants. Our culture has helped us to adapt. We have made clothes and built houses, cultivated plants and domesticated animals to obtain stable food sources.
We have built boats, cars and aeroplanes to explore the world. We have invented medicines to help with injuries and illnesses. We can even survive in space. We have made our environments safe and reduced the stresses that push other species to adapt over time. Knowledge and culture change our environment and are thus also what drives our development further. The question is how the way in which we live today will affect the development of our species in the future.
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Remnants of evolution
Our body still has traces of previous traits that we no longer need.
Ear muscles
Muscles around ears help cats or dogs direct their ears towards sound. Some people can «wiggle» their ears, but this is not very useful for us anymore.
Arm muscles
We have an underarm muscle that has become completely redundant, since we no longer climb trees. 14 percent of people lack it completely.
Appendix
Although we don’t need the appendix to survive, it isn’t completely useless. It can play a role in healthy gut bacteria.
Vomeronasal organ
Many animals use this organ to detect chemical substances. We don’t know if this still works for us.
Wisdom teeth
Four extra molars were useful for our ancestors, who had larger mouths and coarser diets. We don’t need them, and some people lack them all together.
Coccyx
The human foetus has a tail, but it disappears before birth. We are therefore left with a short tailbone.
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Vrakgods fra evolusjonen, en illustrasjon av hva Kroppen vår har spor av tidligere egenskaper vi ikke trenger lenger
Sources:
- Historien om mennesket junior (2020)
Orage Forlag AS
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