Humans Came From Fish

These are some notes for module one. They are not really useful, to be honest, other than as notes for open-book quizzes. The class is more interesting and fun if you read the lectures and not my note

The History of Life on Earth

The earliest evidence of life on earth is dated for around 3.5 billion years ago. As we learned in our high school science classes, we (in terms of humans) originate from the first eukaryotic cell.

The two major cell types are eukaryotes and prokaryotes.

There are three domains of life, eukaryota, bacteria, and archaea.

Kingdom Animalia

The vast majority of animals are both motile (they move around) and they are heterotrophic (meaning that they need to eat.) The majority (around 90 percent) are invertebrates, meaning that they do not have an internal skeleton. Furthermore, 90 percent of all vertebrates are mammals, and most are fish.

Mammals

There are four major groups of mammals.

• Eutherians (placental mammals)

• Marsupials (pouched mammals)

• Monotremes (egg-laying mammals)

  • Only two exist, the platypus and the echidna.

• Multituberculates (the extinct mammals)

  • These goons were actually pretty evolutionarily successful! They lived for a long time before they died out.

  • They appear to have gone extinct because they were outcompeted by mice.

Eutherians and Marsupials actually share a pretty close common answer (in terms of time).

There are 23 orders within the mammalia, of which we share a most recent common ancestor with three other orders — the chiroptera (bats — wow they can fly), the scandentia, and the dermopterans (lemurs).

The Origins of Mammals

Mammals are thought to originate from the allegedly nocturnal creature, Hadrocodium. They were warm-blooded (homeothermic) and lactated. A distinguishing characteristic was that they had (internal gestation) development inside the mother rather than completely in an egg.

There was a large temprature spike during the paleocene, allowing the tropics, and therefore primates, to spread.

Heterodonty was an important evolutionary advantage. Their teeth were all different, meaning that they were able to adapt their diets easier making them more likely to survive.

Presentism in Biology

When looking at human biological history and biodiversity, it is important to consider that we are biased towards the present in terms of our experience with other living things, and it is important to consider not only the present, but the history of biodiversity, in order to form a better understanding of how we got here.