Genesis as Told by Science Part III

The evolution from bacteria to primates

All of life’s diversity around us, so beautiful and so ugly. The way they interact with each other, so elegant and so horrific. Our curious minds demanded an answer, and explanation to all of this mayhem. Is it God who created each and every single life form? all bacteria species, fungi, algae, plants, animals? it seemed like the logical answer, since all creatures appeared static and unchanged, which we know now isn't true. Moreover, we now know from the fossil record that 99% of all species got extinct before humans had even arrived. what a waste, why would God go through such a redundant effort. Was it trial and error? No, the more logical answer is that all life forms are simply products of the same process, evolution. A process that describes and explains perfectly the diversification of life. A process that is supported by heaps of undisputed evidence, making it a fact that can be denied only by people who didn't read evolution or read evolution and didn't or won’t understand it.

Earth is now 500 million years old, the line of the first page of human story is being written, life as we know it is coming to existence, the transition from chemistry to biology is taking place. This seed will grow into a massive life tree, giving rise to intelligence and consciousness. The beginning was with the chemical interaction between hydrogen, oxygen, nitrogen, carbon and phosphorus to form a chemical molecule “DNA”. How? No one knows, it is still one of the most challenging questions that faces science. However, many hypothesis are presented in an attempt to answer the question, like early RNA world, abiogenesis, extraterrestrial seeding and entropy.

Two characteristics of DNA make life possible; storage of biological information, and self-replication. Biological information is stored in the form of genes and serve as an instruction manual for building different kinds of proteins. Self-replication allows the molecule to multiply and pass the biological information to later generations. All life forms, beginning with bacteria and ending with humans, operate in the exact same way, just like all cars since the first model to the latest operate on internal combustion engine. All life operate on DNA; genetic information act as template to transcribe RNA, RNA is used to sequence amino acids within proteins.

With the first life coming into existence, evolution kicked in and started working its magic. As described above, life basically is DNA replicating, and transferring its biological information (genes) to future generations. However, sometimes when the DNA replicates, errors occur while copying the genes (mutation), thus later generations inherit different information making them slightly different. With the passing of multiple generations, enough errors will have accumulated rendering the DNA essentially different from its ancestor. Thus, creating a new specie (Speciation). Sometimes, mutations could be harmful, making life form malfunction in the environment it lives in. Therefore, it dies and all its generation with the same mutation die off too (Extinction).

We can reason out that all living organisms share a universal ancestor, due to the biochemical mechanisms common to all living life forms. The earliest known organisms for which fossil evidence is available are simple bacteria (Prokaryotes) which are 3.8 billion years old. Those early bacteria lack a true nucleus, and didn't use oxygen to perform metabolism to extract energy. In fact, oxygen was toxic to all living creatures at that time.

800 million years later, bacteria which performs photosynthesis appeared. Those bacteria use sun light to chemically create sugars from carbon dioxide and water, and releasing oxygen as a waste. The oxygen initially is captured by iron in the oceans. With time, all iron had interacted with oxygen and became saturated allowing the produced oxygen to accumulate in the atmosphere. This had led to the Great Oxygenation Event or the Oxygenation Catastrophe 2 billion years ago, the high concentration of oxygen caused the mass extinction of most life forms on Earth. Those bacteria were therefore responsible for one of the most significant extinction events in Earth’s history.

1.8 billion years ago, complex cells appear (Eukaryotes). They contain true nucleus, where DNA is enclosed within, mitochondria and other more advanced biochemical operations. They consume oxygen and will be the bases of all multicellular organisms.

2.6 billion years after the first single-celled bacteria, simple multicellular life forms evolve. Those simple organisms will later evolve into plants, animals, fungi, and algae.

540 million years ago, the Cambrian explosion takes place. The tree of life starts branching in all directions in a very short time. For over than 2 billion years life was restricted to simple bacteria, then in a period of 70 million years, life just exploded and complex animals started appearing in the fossil record. It has evolved rapidly into most of the major animal groups that survive today. Trilobites, and crustaceans (ancestors of shellfish; lobsters, shrimps, crabs) appear. Shortly after, the ancestors of octopuses and cuttlefish appeared.

Around 530 million years ago, first jawless fish appeared. Evolved from simple sea squirts (sac-like filter feeders attached to corals) all our current human features; jaws, eyes, face, vertebrate and 4 limbs first emerged with fish and passed on to humans over a long line of evolution and inheritance.

Earth is almost 4 billion years old, life emerges from water for the first time, and it starts colonizing land through primitive plants that evolved from algae. They are the predecessor of all the greenery we see today.

Shortly after, almost 400 million years ago, insects evolve from arthropods (ex. Crustaceans) and radiate through land. Insects, lobsters and shrimps are actually cousins.

385 million years ago, lob-finned fish appeared in shallow waters, with two pairs of fins in the abdominal part of the fish covered by muscle and skin. They are the ancestor of all four-limbed (Tetrapod) animals; reptiles, birds and mammals. They have evolved gradually, developing fins with bone structures similar to the bone structure currently in our limbs. The fish used those fins to walk underwater. Later, air bladders used for buoyancy evolved into lungs.

365 million years ago, a lob-finned fish forsook water aiming to colonize the land. A small step for fish, a huge leap for all land species. This moment will lead to dinosaurs, birds, mammals, and eventually humans. And this is the reason why all mammals have strictly five digits, because the first tetrapod that emerged from water had five digits fins.

30 million years later, first reptiles emerged from the first land dweller tetrapod. After almost 10 million years, first primitive mammals separate from reptiles.

250 million years ago, the most severe extinction event ever befell on Earth. Wiping out up to 96% of all marine species and 70% of land species.

220 million year ago, the earliest dinosaurs appears (prosauropods) it starts a small reptile and over the next 150 million years, they will evolve and diversify due to various pressure points, eventually dominating the planet culminating in Tyrannosaurus-Rex. The raptors branch will later evolve feathers, becoming the first feathered dinosaurs, eventually giving rise to the first birds almost 150 million years ago, which makes birds the only living members of dinosaur family.

66 million years ago marks the end of the age of dinosaurs. A massive commit hits Earth in the Yucatan peninsula causing the K-T extinction event eradicating about 85% of all living species, killing with it all dinosaurs and putting an end to their reign. This has left a huge room for mammals to spread their wings (sort of speak) they radiate and diversify, becoming the dominant species.

60 million years ago, the earliest true primate emerged from tree dweller ancestors. Primates include lemurs, monkeys, apes and humans. During the next 55 million years, mammals will evolve and diversify into rodents, bats, giraffes, bears and all the other known mammal species we grew to love.

In the next article I will cover the human evolution from the common ancestor with monkeys to rise of the Homo sapiens, to us.