Day 42 Human Evolution

History of Life Recap!

The History of Life

(Some of this information is hypotheses based on strong scientific evidence but cannot be proven due to the fact that it happened a very long time ago and cannot be repeated)

Before the 1600's it was thought that spontaneous generation was possible

-Spontaneous generation is when an organism can just appear out of nowhere

-This was disproved in 1668 with an experiment with meat and maggots

So the first cell hypothesis goes like this...

The first living cells on earth were here around 3.8 billion years ago

-The earth was very different 3.8 billion years ago

-The earth had very little oxygen on it

-The earth was full of methane, ammonia, hydrogen, and water vapor

-There was a lot of electricity in the air, lots of lava, and volcanoes

-The earth was very hot

-In these early earth conditions it could be possible for the macromolecules necessary for cells to be created.

-In lab conditions that simulate early earth atmosphere amino acids were created

-So the hypothesis is that under early earth conditions there were pools of organic molecules

-These organic molecules were surrounded by drops of oil creating the first protocells

-Once the protocells could self replicate using RNA they were considered living

-The first cells were prokaryotes

-These prokaryotes floated around, some preditory eating other prokaryotes

-Others were photosynthetic like the Cyanobacteria we have today

-The first Eukaryotic cell came about through a process known as endosymbiosis

-If you remember mitochondria and chloroplast have their own DNA

-This is evidence for the endosymbiosis hypothesis

-Now the earth has both prokaryotes and eukaryotes

-Colonies of eukaryotes became the first multicellular plants and animals

Organism complexity continued to expand into all the groups that we see today

Human Evolution

A Hominin is a human like organism

-We were not the only Hominins on this planet but we are the last

Humans and Neanderthals lived together at the same time

-It is hypothesized that humans killed off the Neanderthals

Humans are an African Species. Here is a chart of their migration from Africa

The first Hominins were on the planet around 6 million years ago. The first Homo sapiens have been on the planet less than a million years

We will talk more about human ancestors when we work on Phylogeny next week