The Universe Revealed

How did we evolve?

How did we evolve?

This is a very complicated question for science because there are lots of conflicting theories about how it occurred. Wiki says that it went like this: Approximately 4 billion years ago life appeared in the oceans. Cells that could employ photosynthesis appeared around 3.9 billion years, but it wasn't until 2.5 billon years that life evolved that could use oxygen. Around 2.1 billon years, more complicated life appeared, known as Eukaryote, which is the precursor for plants like algae and fungi. At approximately 1.2 billion years, sexual reproduction evolved, which resulted in much faster evolution. Something (choanoflagellates) that became the ancestor for animals appeared at 900 million years ago. This was a life form that could move around. However, it wasn't until 600 million years ago that a multicellular (contained different kinds of tissue) animal evolved, but it was only like a sponge. Around 580 million years, animals (cnidarians) could move. In other words they had muscles. The next step was flatworms that had brains. This happened approximately 550 million years ago. More complicated worms evolved around 540 million years ago, and they had hearts and a circulatory system along with gills for breathing under water.

Chordates were the next big evolutionary step around 530 million years ago because they had a skeleton, which eventually led to a vertebrate at around 505 million years ago, which led to a Placodemi, a prehistoric fish, at 480 million years. Then it gets much better with the appearance of Tetrapods, basically things with fins and then legs at 390 million years. The first amphibians appeared around 365 million years and they developed true legs and lungs that evolved into reptiles at 300 million years. This led to egg laying creatures as well as insects. This is very important because the Amniota appeared around this time. This creature could reproduce and lay eggs on dry land.

Mammals appeared about 256 million years ago. This was a branch off of reptiles. Mammals keep the egg inside and give birth the way we do. Eventually, the earliest mammal led to a common ancestor (Euarchontoglines) of mice and men around 100 million years ago.

The precursors to Primates, which is what we are, appeared around 85-65 million years ago. These were small rodent like mammals that ate insects and were nocturnal. At around 63 million years ago, things that resembled monkeys and apes appeared and many branches started. Note that this is several million years after the destruction of dinosaurs by an asteroid collision. In other words, an asteroid collision in the Yucatán cleared the way for our evolution.

At around 15 million years ago, the first Hominidea (Great apes) appeared. These are the precursor to us in the form of the Hominina, the last common ancestor of chimpanzees and humans that appeared around 7 million years ago. In other words, this is where human evolution branched away from that of the apes, or so they believe. Remember that this timeline is based on fossils, but the fossil record going back for several million years is sketchy at best, and when it comes to human evolution, it's downright difficult because there weren't that many hominid creatures running around, so their fossils are rare.

The first hominin (Ardipithecus) like creature appeared around 4.4 million years. However,  Australopithecus appeared around 3.6 million years ago. This is the granddaddy of the homo line, which appeared in East Africa at 2.8 million years. Homo habilis (the tool maker) was the precursor to Homo erectus, the first hominin that walked upright. Homo erectus resembled a human and had a fairly large brain. These appeared around 1.8 million years. Homo antecessor is the common ancestor of humans and Neanderthals, and it appeared in 1.2 million years. Modern Homo sapiens appeared somewhere around 200 thousand years ago. So, you can see that it was a long and torturous journey for evolution to produce us humans.

Recently, a new homo species was discovered. It was found in a cave in South Africa and has been called Homo naledi. Remember that Homo is the genus that we belong to. The good news here is that they found many bones, giving them a complete skeleton of this new species. These creatures are pre-human and had feet and hands like us, and probably walked with a similar gait. However, their skull size is much lower than ours, meaning that their brains were not nearly as developed. At this point, the significance of this discovery as to human evolution has not been ascertained.

There are many factors that contributed to the development of intelligent creatures on Earth. One of these is the fact that early species learned how to make tools. This required the evolution of a marvelous appendage known as the human hand with its opposable thumb. Early humans could hold object into precise orientations and complete operations that would have been difficult for an ape. The human brain, which uses up most of the oxygen and nutrients, developed because of this tool making evolution and the consumption of meat, which supplied plenty of nutrients. These two developments came together to produce us.

Could evolution have created intelligence by another process? That's a good question, and its answer has significance for the evolution of intelligence on alien worlds. Stay tuned!

Thanks for reading.