Macroevolution is the 3.8 billion year history left by Microevolution. What it tells us is that all life on this planet belongs to one great family tree. Over time microevolutionary changes created speciation events that form the branch points on this tree of life. The history of life is marked by significant events such as mass extinctions – like the infamous meteorite impact that wiped out all of the non-avian dinosaurs, as well as major changes in the organization of the information structure of life.
Speciation events, that is one species diverging into two (or more) separate species, has created the tree of life which describes the relationships between all living things. Some are more closely related than others, we are most closely related to chimpanzees, but what evolution tells us is that we are also related to fungi, plants, fish and all other forms of life – if you trace our history back far enough. We can infer the history of life by studying morphological and genetic differences between lifeforms. This is aided by looking at the plants and creatures preserved in the fossil record.
Here are some major events in the history of life:
The origin of life – 3.6 – 3.9 billion years ago
Single celled photosynthetic bacteria begin to fill our atmosphere with oxygen – 3.5 billion years ago
Eukaryotes and meiosis (organised sex) – 1.5 – 2.5 billion years ago
Multicellular life arises – around 1 billion years ago
The body plans for most life appear (with a few exceptions) – 550 million years ago
Our ancestors invade the land – 360 million years ago
95% of all life goes extinct during the Permian extinction – 248 million years ago
The arrival of the dinosaurs – 225 million years ago
The end of the dinosaurs – 65 million years ago
Anatomically modern humans arrive – 130 thousand years ago
We occupy a very tiny fraction of the history of life. If you were to condense the entire 4.6 billion year history of our planet down into a single year, a human lifespan amounts to little more than 0.5 seconds. It’s hard to comprehend how long the history of life is, the main thing to understand is that it is more time than you can imagine. We shall go into more depth about the history of life in another article. That’s it for now.