Australian Science Illustrated — Issue 54 2017

76 | SCIENCE ILLUSTRATED

T

he first primates crawled about 65 million years ago,

in the time of Tyrannosaurus rex, according to genetic

studies of modern animals. But scientists have still not

discovered the remains of the early primates, as the oldest

known fossils only date back from the time after the

disappearance of the dinosaurs.

No matter when the ancestor of the primates lived,

scientists know that the family tree soon branched out in

two. One branch led to strepsirrhini, including lemurs and

lories, whereas the other branch, in which we belong, led

to true monkeys. So far, scientists have not found many

fossils which can help them understand this, but one

single animal sheds light on the matter. Eosimias, which

only weighted 100 g, was so small that it could sit in a

human hand, but it still had a lot in common with us.

Eosimias’ heel shows signs of a transition from feet

designed for long jumps (lemur behaviour) to feet which

were primarily used to walk on branches. This very

characteristic shows that Eosimias was presumably an early

type of monkey. Consequently, the small animal probably

had a relatively large brain and excellent colour vision just

like its descendants. Colour vision is rare among mammals,

and Eosimias most likely used the new characteristic to find

colourful fruit among the leaves of the trees.

Early monkey gave us:

Opposing thumbs

Nails

Eyes with colour vision

An even larger brain

Small Monkey Gave Up Jumping

Meat grilled over a fire

started an evolution that

ended with a unique

species of super intelligent,

hairless ape.

F

ire might be the reason

why we have large brains.

Over the past 1.8 million

years, the size of the human

brain has more than doubled,

and according to some

scientists, this is due to our

unique ability to prepare

food over a fire.

It is difficult to extract

calories from raw food, which

requires large quantities of

energy to digest, but fire can

take care of the hard work for

us, making more calories

available to the brain. The

oldest known indication of the

use of fire is, however, only

about one million years old, so

new discoveries are necessary

to confirm the link between

fire and our growing brain.

The result of the fast

development is a brain which,

with its 1,350 cm^3 , is more

than three times larger than a

chimp’s. The extra brain cells

have ensured improved

control of our larynx and

so provided us with our

perhaps most important

capacity: language.

Cooked Food Gave

us Large Brains

Mouth

Just like us, sea cucumbers

have mouths, which they use to

consume food. However, sea

cucumbers take one step further

with tentacles, which can

capture the food.

Bowels

During the embryonic stage of

sea cucumbers and humans, the

anus develops first, followed by the

bowels and the mouth, as opposed

to other creatures such as insects

and molluscs. Moreover, some sea

cucumbers have gullets and

stomachs just like us.

Muscles

Sea cucumber muscles are simple,but

they still consist of both skeletal and

smooth musculature just like ours. Sea

cucumber muscles let the body can

contract and the tentacles can be moved.

Nervous system

Sea cucumbers have

a central nervous

system: a ring of nerves

around the mouth, and

more nerves lead to the

rest of the body. These

nerves are produced by

supporting cells just like

in humans.

You Look Like a Sea Cucumber

We share a 450-million-year-old ancestor with sea cucum-

bers, and the family resemblance is still evident.

45 million years ago

Now

CLAUS LUNAU

HUMANS EVOLUTION