The genetic accident behind all life on Earth

Deep blue: The sea sponge is the oldest species still found on Earth.

A new scientific study has found that 600 million years ago, a single cell mutated and Earth was changed forever. A dazzling range of complicated animals would follow. Could it happen again?

Eyes which can see a full spectrum of bright colours (but not ultraviolet, enabling colour night vision). Noses with a sharp sense of smell (but not nearly as sharp as dogs). The ability, for most Europeans at least, to drink milk after infancy. And, first spotted in Burkina Faso in 2001, a resistance to malaria.

Each of these is the result of genetic mutations, which have been driving human evolution for millions of years. As humans evolved, so too did a diverse and spectacular animal kingdom. Long before that, some dinosaurs developed feathers and hollow bones which helped them take to the sky as birds and survive the extinction of their ancestors. In the sea, where all this life began, there are so many species that between one and two thirds are still unknown.

Now a group of scientists at the University of Oregon has traced all this evolution back to a single mutation 600 million years ago. The team was studying choanoflagellates — tiny organisms thought to be our closest single-celled relatives — and was able to ‘resurrect’ the genome of their ancestors. The scientists were amazed by what they found.

The story goes like this: protozoas, single-celled organisms with ‘animal-like’ behaviours, were once as lively as the oceans got. Then, a certain protein mutated from an enzyme into something called an interaction domain. This allowed the organisms to begin communicating and working together as a group.

From here, multi-celled organisms were born — and complex life could begin. According to the scientists behind the study, these same proteins are now found in every animal on Earth, helping their cells to stay in contact.

‘It was a shock,’ said one of the lead researchers, Ken Prehoda. ‘If you asked anyone on our team if they thought one mutation was going to be responsible for this, they would have said it doesn’t seem possible.’

Freaks of nature

This miraculous event proves life on Earth unique, some conclude. From a single mutation, at the perfect moment, on a planet which just happened to have the right combination of warmth, carbon and oxygen, came this incredible array of complicated creatures. The circumstances were so unlikely. There may be simple forms of life on other planets, but surely Earth must be alone.

And yet the universe is very, very big. It might even be infinite. It contains billions of stars, circled by billions of planets. For that reason, many physicists argue that there is a good chance complex life could have evolved on one of them, just as it did here. It is illogical, even arrogant, to think that because it has happened once — on our planet — it could not happen again. What would that life look like? Now there’s a question.

You Decide

  1. Genes are the building blocks of the human body and what it can do. If you could choose one mutation, what would it be?
  2. Does the discovery of one single event which created complex life prove the existence of God?

Activities

  1. Draw and label an alien life form that has evolved on another planet. What features does it have? What are they for?
  2. Use the links under Become An Expert to research a genetic mutation which has had an impact on human evolution. Write a paragraph explaining what happened and why it mattered.

Some People Say...

“I don’t believe that there are aliens. I believe there are really different people.”

Orson Scott Card

What do you think?

Q & A

We’ll never know the answers to these questions. What’s the point?
Not necessarily — the Search for Extraterrestrial Intelligence (SETI) Institute has dedicated itself to searching for the technology ‘signature’ of other intelligent life. Even if it is unsuccessful, the question is worth pondering anyway — it has the power to change the way we think about ourselves, our planet, and the creatures we share it with.
I thought evolution happened through natural selection.
That is the most widely-known theory, and it may still be true. Scientists who study genetic evolution would argue that mutations happen randomly; some are good, some are bad, others make no difference. ‘Survival of the fittest’ may decide which mutations stick around, but it’s the genes that make the first move.

Word Watch

Europeans
Most mammals stop digesting lactose when they have been weaned off their mothers. But in Turkey, around 10,000BC, a genetic mutation changed all that. It quickly spread across Europe. Around 80% of Europeans can now drink milk. Globally, the proportion is 35%.
Burkina Faso
A small country in West Africa. In 2001, researchers found that some of the population had gene variations which reduced the risk of malaria by 93%.
Mutations
A permanent change in the DNA sequence. Mutations can be passed on by parents or caused by environmental factors such as radiation, or they can be completely random.
One and two thirds
The same analysis which made this estimate — completed by Unesco in 2012 — suggested that there were between 700,000 to one million species in the sea. For obvious reasons, it impossible to give an accurate number.
Genome
A complete set of an organism’s DNA, including all of its genes.
Protozoas
Single-celled organisms including amoebas, which can change their shape, and flagellates, which have ‘whip-like’ appendages to help them to move.

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