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“It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn't feel like a giant. I felt very, very small.” – Neil Armstrong (1930-2012)

Fresh Reads from the Science 'o sphere!

Sunday, November 18, 2007

The Descendants of Man

Human beings have been on Earth for less than 500 000 years.

Though some wackos believe that people are specially-made creations from an intelligent deity (who created the entire Universe for us), the reality is that Homo sapiens, like all life on Earth, emerged from a long process of biological evolution.

There is evidence that human beings have been evolving since our ancestors first stepped out of Africa.

But are we continuing to evolve? I know one professor who believes that human beings are no longer evolving.

There are some reasons why this could be the case.

We have eliminated many selection pressures on the global population, such as childhood mortality due to infectious diseases, which could cause gene frequencies to change quickly. Consequently our population size continues to grow at an increasing rate.

In addition, at 6.5 billion strong, there are so many people that neutral drift will take a long time to have a significant effect.

(Actually, the current effective population size per generation (Ne) of human beings is less than 10 000, because we nearly went extinct about 100 000 years ago. Even so, using Ohta and Kimura's formula, a neutral gene will become fixed in the global population in 4 x Ne generations = 800 000 years!)

Suffice to say that in our current environmental and genetic landscape, we aren't evolving much at all.

But environments are changing and new mutations are popping up all the time.

If a group of people were to become reproductively isolated from the main population for many thousands of years, and experience a drastically different living environment, then they could evolve into a new species.

A descendant species of Homo sapiens!

Fresh Brainz is proud to bring you the first in a series of speculative art about the descendants of man.

But first - getting the right tool for the job. My old drawing tablet had been giving me trouble for weeks and it's time to get a new tablet.

Looks more business-like eh?

Now back to the story!

Imagine a dark, scary place that never sees the light of day, but contains a plentiful supply of food.

A small population of animals venture inside to feed, but most of them never managed to find the way out.

Since it is completely dark, they need to depend on their sense of touch to navigate this new environment. Eyes are useless.

Many generations are born, reproduce and die inside. Gradually, the offspring that have the best sense of touch became more successful at surviving and reproducing. The genes that are involved in touch are highly favoured over genes that are involved in sight.

As a result, their eyes disappear.

Is this a true story? Here is a real-life example!

Mexican cavefish lack eyes because the protein involved in enhancing their sense of touch in the lower jaw, called hedgehog (Hh), suppresses the expression of a gene important to eye development, pax6.

In addition, they have larger jaws, maxillary teeth and taste buds than other closely-related species. They also lack melanin pigments in their skin.

Human beings also have hedgehog (such as indian hedgehog in chromosome 2 and sonic hedgehog in chromosome 7) and pax6 (chromosome 11) genes.

So - what would happen if a group of people were to be stuck in a subterranean enclave for many generations?

You are thinking: "Why would anyone want to live in a cave?"

Maybe there's a nuclear war raging up there (probably started by the same wackos mentioned earlier).

Maybe there's an abandoned military food depot down there.

Maybe they just want to be left alone.

Whether by plan or accident, a large group of people find themselves in an underground network of caves, seeking protection from the chaos above.

Initially dependent on technology to stay alive, the batteries eventually run out.

Then canned food supplies get depleted and the survivors are forced to explore the caves for natural food sources, which is surprisingly abundant and accessible.

A few hundred thousand years later...

Introducing the blind cave hominid - descendants of the ancient human race.

They can't see, but their other senses are tuned into overdrive.

Increased sensitivity to touch, hearing, taste and smell allow them to explore their habitat with ease. Like the cavefish, these hominids have a strong jaw and robust maxillary teeth to chomp down on the non-industrially processed food of the future.

They also have a smooth, glassy complexion - without pigmentation, their skin appears translucent with all the surface blood vessels visible.

Of course, by "visible" I mean visible under light, which is irrelevant to them.

As such, visual appearance is meaningless - the hallmark of a sexually attractive mate is the tactile flawlessness of their skin, and the pheromones they produce.

In order to effectively feel their way around their underground environment, cave hominids crawl close to the ground and listen attentively to their surroundings.

If they encounter another hostile cave animal, they will signal to each other in high-pitched, near ultrasonic shrieks that echo throughout the caves, recruiting more tribe members to join in the fight. They have a complex, hierarchical social organization that makes them deadly towards other animals, and to members of rival tribes.

I don't know about you, but I wouldn't want to be there when a few hundred irate cave hominids turn up to greet an unwelcomed visitor.

Even if you have phasers or whatever.

Would you like to know more?
- Jeffery Lab (University of Maryland research lab, focusing on cavefish evolution)
How the cavefish lost its eyes (by PZ Myers)
- Man after man (by Dougal Dixon - speculative science fiction book. I haven't read it, but it doesn't appear to have details at the molecular level.)


Teh Si said...

I think intelligence as we understand it in the cave-scenario will quickly deteriorate . What a pity!

Nice drawing btw! Sure hot chicks will be impressed!


Lim Leng Hiong said...

Thanks for the compliment! Though I doubt that hot chicks are impressed by drawings.

Since we do most of our learning with our eyes, yes, intelligence will take a dip initially.

But as the cave hominids switch to other senses for learning their intelligence becomes anyone's guess.

The Flying Trilobite said...

Hot chicks are impressed by drawings. I married one. (A hot chick, not a drawing).

Man after Man is really good. the illustrations are excellent throughout. When it starts off, it is easy to be excited by the more intentionally designed and exotic forms of humanity. By the end though, I found myself nostalgic for us old style humans. Everything had changed so much, and so much biodiversity lost, one kind of human preys on another.

Lim Leng Hiong said...

To Glendon:

Thanks for the encouragement! Of course I'm happy that you found a hot chick who is impressed by your drawings, but things are tad different around here...

Oh and that's a intriguing summary of Man after Man. I'll try to find it in a public library and take a look.