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Can you explain human evolution?
Question Date: 2018-02-08
Answer 1:

That's a big question, but evolution works about the same in all living things. Generally, it happens as a result of natural select.

Individuals in a species are genetically different from each other (unless they're clones). Some of the differences give an advantage that allows those individuals to leave more offspring, which then have the genes of their parents. Over time, the helpful genes become more common. The differences between individuals are the result of random mutation. The selection part is non-random.

In humans, some of the trends that gave individuals an advantage seem to be increased brain size, walking more upright (which allows hands to be less foot-like), and a mostly hairless body. Individuals with random mutations that gave them these characteristics were more likely to leave offspring.

We are not descended from chimps, gorillas, monkeys, or any other living primate, but we share a primate ancestor that had opposable thumbs. The descendants of the first primates split over millions of years into many different types of primates. Some are extinct. Some are still around. The first humans evolved about 200,000 years ago, but there were other lines that had some of our characteristics but died out.

Why do you think humans are so successful while our closest relatives are often threatened or endangered?

Thanks for asking,

Answer 2:

Thanks for the great question!

While many people before him thought animals change and evolve over time, it was Charles Darwin who determined how evolution works. Darwin’s idea is called evolution by natural selection. Animals of the same species, Darwin observed,

(1) have to compete to survive,
(2) exhibit variation (in size, coloration, behavior, etc.), and
(3) pass down their traits to their offspring.

It was those animals that fit best in their environment that were able to survive and reproduce the most, and so the traits of those fit individuals spread throughout a species. Over time, certain traits die out and others survive. With the accumulation of new traits, entire new species evolve. Hundreds of years of research, especially modern genetics, have since supported and elaborated on Darwin’s original idea.

Humans are a result of evolution by natural selection . Biological anthropologists and evolutionary psychologists, including those at UC Santa Barbara, study human evolution .

About six million years ago in Africa, due to the changing climate at the time, the ancestor of modern humans split from the linage that would eventually evolve into the chimpanzee. These human ancestors were unique in that they were bipedal, they walked primarily on two legs, and had increasingly larger brains for the size of their bodies. These early human ancestors include Homo habilis, the first to use tools, and Homo erectus, who spread out across the world about two million years ago. H. erectus used tools and fire and lived on Earth until only 140,000 years ago!

Anatomically modern humans, Homo sapiens, evolved from the same linage of these ancestors about 200,000 years ago. Humans quickly migrated out of Africa and colonized the world, reaching as far as islands in the middle of the Pacific Ocean some 50,000 years ago. Other species of the genus Homo, like the Neanderthals in Europe and Eurasia, went quickly extinct with the arrival of H. sapiens , likely because of modern human’s superior intelligence and communication abilities. Humans evolved to exploit their environment using their brains, and eventually, human brains started creating culture, science, art, agriculture, civilization, and all the rest.

Thanks again for the great question,

Answer 3:

Human evolution is the process by which modern humans (us) have come from our ancestor organisms through many years of adapting to our environments. To become Homo sapiens, our entire bodies have changed from the DNA-level up. Not only have our genes themselves changed, but how they turn into RNA (cellular messengers) and proteins (cellular machinery) has changed, too. It is a slow but fascinating process because as different as we look and behave from other animals such as chimpanzees, only about 1% of our genome (complete set of genes) is different from the genome of the chimpanzee! This small difference simultaneously showcases the essential components of life (the high percent similarity) AND the subtle cellular and organismal adaptations that go far beyond simple changes in DNA.

The theory of evolution (with high volumes of compelling evidence) indicates that adapting to our environments in order to become the humans we now are required long periods of exposure to these environments, and many iterations of the selection processes in which the organisms that can most quickly begin to use their environments in the best ways live longer and produce offspring that then propagate. The organisms that do not adapt as quickly or readily eventually give way to the optimal organisms, and that is how we modern humans came to be. However, as supported as the theory is by evidence, many questions remain as to how exactly we became humans - scientists are actively studying all steps leading from simple single-cell organisms to humans.

Thank you!

Answer 4:

I could probably keep explaining human evolution for most of the rest of my life. Part of the reason it would take so long is that new research keeps discovering new things about human evolution, so then I'd need to add that new research to my explanation.

One thing I learned recently about human evolution is about Vitamin C. I thought that all the animals except humans and guinea pigs could make their own Vitamin C; the other animals don't need to eat it as a vitamin. But it turns out that non-human primates also don't make their own Vitamin C, which fits with the fact that we and the non-human primates share a common ancestor. That common ancestor was probably a primate that lost the ability to make its own Vitamin C. Some ancestor of guinea pigs probably also lost the ability to make its own Vitamin C. But other rodents can make their own Vitamin C, so the guinea pig ancestor that lost the ability to make its own Vitamin C must have been an ancestor of the guinea pig but not an ancestor other rodents.

Guinea pigs are domesticated animals that descended from some guinea-pig like rodent in the Andes in South America. I wonder if the wild ancestor of the guinea pig needs vitamin C. I could probably find out if I looked hard enough on the internet, but I'll not do that now.

I'll suggest that you google 'human evolution' and read what Wikipedia and some of the other links say. I hope you find what you want!

Answer 5:

Only partially - there is a lot that we still don't know.

Humans are members of a family of apes called the Homonidae, which includes modern humans (Homo sapiens), chimpanzees (Pan troglodytes), bonobos (Pan bonobo), and two species in the genus Gorilla (I do not know if either of them have common names apart from just "gorillas"). There are also a great many extinct species in this family.

Humans shared an ancestor with chimpanzees and bonobos between five and ten million years ago. What this means is that there was a species of ape at that time that had two populations, and today's chimps and bonobos are descended from one and humans are descended from the other. That species of ape was neither a chimp nor a bonobo nor a human; it was another species of ape that is now extinct.

The population that gave rise to humans gave rise to many, many species, all of them are now extinct apart from H. sapiens. Of the line that became H. sapiens, they appear to have developed a roughly modern upright walking posture by 3.5 million years ago, but did not develop a modern brain size until about one million years ago. By a million years ago, an animal that could have had children with a modern human certainly existed, because that's when the population that would become H. sapiens and the population that would become H. neanderthalensis (neanderthals) diverged, and people of European descent (i.e. white people) have about 4% neanderthal ancestry. Neanderthals and other human-like species at the time were probably about as intelligent as modern humans, so why they became extinct is a mystery.

Humans are still evolving . Unfortunately, we seem to be evolving in a direction that we would rather not go: more intelligent people are having fewer children than less intelligent people, and as a result humans are over time becoming less intelligent. The reason for this trend is probably social. This will probably lead to our extinction if we don't do something to counteract it (or unless something else causes us to become extinct first, such as war or damage to the environment).

Answer 6:

First, it is important to note that humans are not descended from apes. Rather apes and humans have a common ancestor that existed millions of years ago. It is a misconception to think of this ancestor as a “missing link” along a straight lineage from apes to humans, but rather the ancestor is a node where the ape lineage and human lineage branched off into separate directions.

Human beings (Homo sapiens) evolved from now-extinct primates sometime around 200,000-300,000 years ago. Humans are the only surviving species of the genus Homo but there is abundant evidence in the fossil record to suggest that humans were preceded for millions of years by other members of the subfamily called hominins (now all extinct except for humans) which have various human-like characteristics and co-existed with humans for at least for some time.

Human evolution is pretty complicated but here I will try and provide a very brief timeline of major events in human evolution (the dates are approximate).

500 million years ago Evolution of the vertebrates - The early vertebrates are the ancestors of all fish, amphibians, birds, reptiles, and mammals. The distinguishing feature of vertebrates is a backbone which basically makes it possible for vertebrates to have a nerve cord running along the length of the animal and providing a central nervous system.

400 million years ago The rise of the tetrapods (four-limbed vertebrates) - The first tetrapods were aquatic but eventually moved onto land and are the ancestors of amphibians, reptiles, birds, and mammals.

300 million years ago Amniote evolution - The next major evolutionary event was the development of the amniotic egg, and allowed reptiles to move farther onto land, away from the water.

65 million years ago – 1.6 million years ago explosion of mammals. Major developments in mammalian evolution include the evolution of placental mammals which can give birth to live young. Earliest primates also evolved during this time.

13 million years ago – Pierolapithecus catalaunicus is the last known common ancestor of all apes and humans. pierolapithecus catalaunicus .

5.5 million years ago -humans and chimpanzees split from unknown common ancestor [S. Kumar, A. Filipski, V. Swarna, A. Walker and S. B. Hedges PNAS 2005 December, 102 (52) 18842-18847. https://doi.org/10.1073/pnas.0509585102]

5-2.6 million years ago early hominins - proto-humans develop. The most important of these is genus Australopithecus, which had a brain-size similar to a chimpanzee. austrolopithecus

2 million years ago Homo habilis - developed from Australopithecus, had some advanced human-like traits. Homo habilis is considered to be the first of genus Homo (man-like) homo habilis .

1.8 million years ago –Homo erectus – human-like body features and used primitive tools, walked upright homo erectus .

400,000 – 40,000 years ago Neanderthals (Homo neanderthaensis) appear in fossil record. Neanderthals populated Europe and parts of Asia and used tools. Humans are not descended from Neanderthals, but they are the closest extinct relative to modern humans.

200,000 years ago first appearance of humans (homo sapiens) in Africa. However, at this point they had not developed art, sophisticated hunting skills, or fishing.

60,000 years ago – “great leap forward” major development in cognitive ability characterized by abstract thinking. Innovation of jewelry, painting, and advanced stone tools, possibly due to vocal box developed or increase in brain size. great leap forward

Humans migrate out of Africa into China and Southeast Asia

45,000 years ago – humans spread across Europe – Neanderthals soon disappear. (cave paintings appear, statues , musical instruments).

15,000 years ago modern humans walk the Bering land bridge and rapidly populate Americas.

11,000 years ago – agriculture develops.

5000 years ago – writing is invented, beginning of recorded history.

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