HOW HUMANS EVOLOVED FROM HOMO ANCESTORS

 

                   HUMAN EVOLUTION

Homo Habilis, homo Erectus, and Homo Neanderthals are the names of some species that were the closest ancestors of humans. Humans have some special relatives called Great Apes. These include chimpanzees, gorillas, orangutans, and us, humans. We all belong to a scientific group called Hominids. One thing that makes us similar is that none of us have a tail. Now, here's something interesting: gorillas and orangutans can walk on two legs like humans, even though they usually walk on all fours. We also share the same blood group types across all Hominids. So, in a nutshell, we humans have some close cousins in the Great Ape family, and we share some common traits with them, like no tails and similar blood groups.

even though Great Apes can't talk like we do, they can understand human sign language, which is pretty cool. Plus, when we tickle them, they make sounds that are a lot like laughter, just like us! Now, the reason for all these similarities is because we share a lot of our genetic material. For instance, humans and chimpanzees have a super high 99% similarity in their DNA. Gorillas come next, with 98% of their DNA matching ours. And our third cousins, the orangutans, share about 97% of their DNA with us. So, these genetic connections explain why we have so much in common with these Great Apes.

In the group of Hominids, which includes humans and Great Apes, we also have some smaller apes called gibbons. There are about 20 different species of gibbons. These gibbons share about 96% of their DNA with humans, which is quite a lot. Now, when we talk about Hominoids, that's a bigger group that includes all of us without tails, like humans, Great Apes, and these gibbons. One interesting thing about Hominoids is that we all have a special vision called trichromatic colour vision, which helps us see lots of different colors. So, no tails and colorful vision are things we all have in common in this big family.

Now, if we take a step back, we have a bigger group called Anthropoids. In this group, we have both monkeys and apes. There are 130 different types of old-world monkeys and 120 types of new-world monkeys that are still around today. So, it's a pretty diverse bunch of primates in this category.

If we go even further back, we reach a group called "primates." In this group, we have not only monkeys and apes but also creatures like Tarsiers and Lemurs. These two are known as "prosimians," which means they are like early versions of monkeys. Tarsiers are animals that are sensitive to daylight, while lemurs are quite interesting because there are over 100 different types of them. Lemurs are actually the oldest primates in the world. Now, when we look at all primates, we notice some common things. One is that all primates have hands that can grab and hold things. We humans are a great example of this. But here's a neat thing: other primates, besides humans, can also use their feet to grab things. So, they have grasping feet! Another cool fact is that all primates have big brains, which makes them smart creatures. So, whether it's using their hands, feet, or their brains, primates are a fascinating group of animals.

All primates, like monkeys, apes, and humans, like to live together in groups. They do this because they enjoy being around others and have complex ways of interacting with each other. Now, when it comes to smelling things, primates aren't very good at it. Compared to some other animals like dogs, our sense of smell isn't that great. Dogs, for example, have an amazing sense of smell, way better than ours. So, smelling things is not our strong suit, but we make up for it in other ways with our social behaviors.

Around 60 million years ago, scientists think that primates first appeared. In 2012, they found some ancient fossils in Montana that were about 65 million years old. These fossils belonged to a creature that looked a bit like a mouse, and it was named Purgatorius. This little guy is believed to be the oldest primate ever discovered. Now, one thing about primates is that they're really good at climbing trees. That's why they're often called "arboreal." A scientist named Jonathan Block has a theory that there might be a connection between the evolution of primates and the plants around during that time. So, it's possible that the environment and the plants had something to do with how primates evolved.

Around 25 million years ago, something interesting happened in the evolution of primates. This is when hominoids came into the picture, and some primates started losing their tails. The earliest ancestor of humans without a tail was a primate called Proconsul. This change happened because of a mutation in a gene called TBXT. Now, why did this happen? Well, it's thought that some primates began to walk on two legs instead of four. Tails are handy for hanging onto trees, but when we're walking upright on two legs, they can get in the way. This way of moving on two legs is called "bipedalism." The very first ancestor of humans to walk on two legs was Ardipithecus Ramidus, who lived about 4.4 million years ago. However, when scientists looked at their skeletons, they realized that they didn't always walk on two legs. They figured this out by studying the bones and how they differed from those of humans. So, while they could walk on two legs, it wasn't their main way of getting around.

Around 3.7 to 3 million years ago, there was a species called Australopithecus Afarensis. These guys were special because they always walked on two legs, making them committed bipeds. In 1974, in Ethiopia, they found a famous fossil of an Australopithecus named Lucy. What's really cool is that they found a bunch of skeletons in one place, which gave us a lot of information. Australopithecus still had long and strong hands, which is interesting. The oldest stone tools made by our ancestors were discovered in Kenya, and they were about 3.3 million years old. In 2010, in the same area where they found many Australopithecus fossils, they also found some animals' bones that were 3.4 million years old. These bones showed signs of being used with stone tools, which tells us that Lucy and her kind were already using tools. But scientists think they didn't make the tools themselves; they likely used sharp stones they found naturally. Lastly, these species were omnivores, which means they ate both plants and animals. So, they had a varied diet.

The first species to use tools was Homo Habilis. They were like the handymen of their time, living around 2.5 million years ago. These early humans were quite short, only about 3 to 4 feet tall. Back then, they sometimes had trouble finding enough food, so they relied on meat a lot. They mostly hunted and ate small animals and also scavenged for food. To help them with this, they used stone tools to cut the meat and scrape it off the bones of dead animals. So, we can say they were the first butchers and tool-users in our family tree.

After Homo Habilis, there was an evolution to Homo Erectus, also known as Homo Ergaster, which means "working man." They lived from about 1.9 million to 0.14 million years ago. Some scientists believe that Homo Ergaster originated in Asia because Homo Erectus was the first group to leave Africa and spread to various parts of Asia. What made Homo Erectus special was that they had better physical and mental abilities compared to their ancestors. They had smaller hands and longer legs. These early humans are credited with being the first to control and use fire. They were also excellent at long-distance running and jogging. They didn't just hunt; they gathered fruits and learned to preserve meat by drying it. Initially, they would take fire from natural sources, but eventually, they figured out how to make fire on their own. So, they were resourceful and skilled survivors.

In South Africa's Wonderwerk Cave, scientists found evidence of controlled fire that dates back over a million years. About 500,000 years ago, our early ancestors learned to cook meat, and this was a game-changer. When they started eating cooked food, they had a reliable source of meat, which gave them more energy. With this extra energy, their brains started to grow bigger, and their digestive system became more efficient. Their teeth even got smaller because they didn't need big ones to chew raw meat. These early humans likely lived in larger groups, and they interacted socially. They might have even had a basic form of language for communication. So, cooking food not only changed their diet but also had a big impact on their brains and the way they lived together.

After all these developments, we finally arrive at Homo Sapiens, which means "wise man." This is the species of humans we are today. Our species first appeared around 300,000 years ago. Now, there's a bit of debate among scientists. Some believe that the Homo Sapiens from that time should be called Archaic Homo Sapiens, and the ones who emerged about 150,000 to 160,000 years ago are what we call Modern Homo Sapiens, similar to us today. What makes Homo Sapiens special is our big brain, which is about 1,350 cubic centimeters in size. This big brain allowed us to think and create in ways that our ancient ancestors couldn't. We started making art and showing evidence of abstract thinking. This creative thinking helped Homo Sapiens spread all over the world, and today, we dominate the entire planet.

Evolution is a bit like a winding path with no set direction. It doesn't go in a straight line from Homo Habilis to Homo Erectus and then to Homo Sapiens. It's more like a complex journey. One of the more recent versions of Homo Sapiens is called Homo Neanderthals. They appeared around 400,000 years ago and lived until about 40,000 years ago, which is quite recent. They got their name because their first fossils were found in Germany in 1856. These Neanderthals lived in places like Europe and Asia where it was really cold because they were in higher latitudes. So, they were adapted to survive in those chilly environments.

Compared to Homo Sapiens, Neanderthals were a bit shorter and had bigger noses. Their hands, feet, lower legs, and lower arms had smaller bones. These differences were adaptations that helped them survive in the cold environments they lived in. Surprisingly, Neanderthals were quite intelligent. They painted in caves, could listen and speak, and even buried their dead in the ground. However, something around 40,000 years ago in Europe led to their extinction. On the other hand, Homo Sapiens like us had a diverse diet. We ate not only meat but also fish and plants, which might have given us an advantage in surviving and thriving.

Neanderthals had a tough time working together compared to Homo Sapiens. Also, there weren't many of them, only about 5,000 in total. When scientists studied their DNA from different Neanderthal bones, they found that their genetic makeup was almost identical to each other. There wasn't much variety in their genes, which was a big problem for their survival. Here's something fascinating: around 45,000 years ago, Homo Sapiens had already made their way to Europe and Western Asia. This means there was a period of about 5,000 years where both Homo Sapiens and Neanderthals coexisted in the same areas.

When scientists studied the DNA of modern humans, they discovered something interesting. There was evidence that Homo Sapiens had interbred with Neanderthals in the past. In fact, many people today have about 2% of their DNA coming from Neanderthals. So, in a way, a part of our ancient relatives still lives on in us. Another important point is that as researchers keep digging up more bones in their excavations, they sometimes find new species. One of these recent discoveries is called Homo Bodonensis.

In the past few thousand years, there's evidence that Homo Sapiens, or modern humans, have evolved. Anthropologists like Nina Jablonski and George Chaplin point to a significant example of this in our skin color. This change in skin color is a result of evolution. Here's how it happened: Thousands of years ago, people who started living in northern areas, far from the sunny equator, developed lighter and whiter skin. This change helped them because in those areas, the sun didn't shine as much, and there were lower levels of UV radiation. So, their skin adapted to these different conditions.

Another recent example of evolution involves our ability to digest milk, known as lactose tolerance. In places like Scandinavia (Finland and Sweden), where dairy farming was common, people have the highest lactose tolerance. This means their bodies can handle milk digestion. But in regions like India (Haryana and Punjab), many people have trouble digesting milk because their stomachs weren't evolved to do so. It's all about adaptation. Those in colder areas went through evolution to adapt to the cold weather, while in regions where dairy wasn't as prevalent, lactose tolerance didn't evolve as much.

In South Korea, over the last century, women have, on average, gained 8 inches in height. This happened because they started getting better nutrition. Taller women tend to have fewer problems during childbirth, so this change in height has been helpful. But keep in mind that these changes happen slowly over a long period of time.

When we talk about evolution, we can start from different points. Some begin with primates like us, while others start with mammals in general. All mammals share certain traits. For example, even lions, tigers, and big whales have hearts with four chambers, just like humans. If we want to go even further back, we can start with a group called Tetrapods. These are animals with four legs. They include amphibians like frogs, reptiles like crocodiles, and even birds like sparrows. So, evolution can be looked at from different starting points depending on what we want to study.

In 2010, scientists decoded the genes of an African clawed frog and found something fascinating. They discovered around 1,700 genes in this frog that are quite similar to human genes, especially when it comes to specific diseases like cancer, asthma, and heart disease. Now, when we talk about vertebrates, we mean animals with spines, like us. Among the 34,000 fish species that live in water, there's one called the zebrafish. Surprisingly, 73% of its DNA matches with human DNA. This makes zebrafish really important in scientific research. In recent years, scientists have been using zebrafish a lot, especially for testing new medicines. They've become a valuable tool for studying human diseases and finding potential treatments.

We can go even further back in the tree of life to a group called eukaryotes. This includes all animals, plants, and fungi. Let's take yeast, for example. In 1996, scientists sequenced the entire genome of yeast, which is a type of fungus. Now, here's something interesting: in humans, when a protein called alpha-synuclein builds up, the risk of Parkinson's disease goes up. Well, it turns out this protein affects yeast as well. In fact, researchers found that at least 20% of the genes in humans that are linked to Parkinson's disease have similar counterparts in yeast. So, studying yeast helps us understand and find clues about human diseases like Parkinson's.

Edward Marcotte, a biologist from the University of Texas, did a fascinating experiment. He found 500 important genes that yeast needs to stay alive. Then, he proposed replacing those yeast genes with similar genes from humans. These are the genes responsible for things like making cholesterol and keeping cells healthy in both yeast and humans.

After three years of experimenting, we discovered something interesting. We were able to replace about half of the yeast genes with the human version. This suggests that many of the important processes that happen in yeast cells are quite similar to those in human cells. Edward Marcotte concluded that around 1 billion years ago, yeast and humans shared a common ancestor. This means that we have some ancient history in common!

Professor Bill Martin from the University of Dusseldorf and his team took a different approach. They studied very old genes from bacteria and archaea and discovered that there were 55 genes that these two groups shared. By tracing back through these genes, they eventually reached a common ancestor they called FUCA.

All life is believed to have started from a tiny cell. This cell was made up of special building blocks called nucleotides. When genetic material from a man's sperm combines with genetic material from a woman's egg, it forms a fertilized egg called a zygote. This zygote begins to divide through a process called mitosis. It goes from 2 cells to 4, then 8, and so on until it forms a small ball of cells. By the sixth day, it becomes a blastocyst. This blastocyst hatches and attaches itself to the uterus, where it starts developing into a baby. The placenta, which nourishes the baby, forms, and eventually, all the major organs and body systems develop—things like the brain, heart, eyes, ears, and more.

Around the eighth week, the developing baby starts to look more like a human, although it's still very small, about an inch in size. At this point, we call it a fetus. Skipping ahead, after about ten months, a human baby is born. This whole process began with a tiny fertilized egg called a zygote. Evolution works somewhat similarly, where small changes over a long time can lead to the development of new traits and species. That's how human evolution happened.

Comments

Popular posts from this blog

Application of Biotechnology in Cancer research

Foundations: How We Feel Hunger and Fullness 🧠

Steatotic liver disease - Causes & Treatment