Have a look at this. It's a bit of a human body
These are cells from the inside of a human cheek magnified thousands of times
they're similar to the kinds of cells all complex plants and animals are built from
Now here's another one of these human cells on its own
See those tiny black marks. They are bacteria
You can see they're thousands of times smaller than my cells, and they're much simpler too
the puzzle is this for the first billion years or so life on Earth consisted entirely of
Simple single cells like Bacteria and Archaea and then suddenly around 2 billion years ago
Complex cells appeared cells more like the ones that make up you and me and it seems they appeared out of the blue
So did life really leap from simple cells to complexity in one fell swoop?
After all we normally think of evolution proceeding in tiny incremental steps
This is a strange
Dichotomy within the theory of evolution and lots of them in a quarrelsome lot
Between what what sometimes called evolution by Jerks versus evolution by creeps, okay?
and I was always a bit of a creep in my time
Which was that actually evolution is a bit like a clock it ticks slowly around and cause it
Speeds up and slows down a bit
the Jerks line was that evolution went slowly most of the time and then whoopee there was a wonderful moment when it took a
Dizzying leap into the void and left over to a new form of life, but actually I hate to say it
It causes me great pain to say this there are some cases where it's clear that a dizzying leap was made in evolution
And the reason we now accept that this and indeed other dizzying leaps can happen is because of what we've learned from studying
DNA
from our and other species genetic code
This is doctor Nick Lane
He studies this puzzling transformation when life went from being simple to complex
It all started with the curious marriage of two simple cells
Two billion years ago or give or take literally and booing is this first complex cell arose?
And it seems to have come about by one cell getting inside another cell really as simple as that
the host cell was probably an Archaea and
The cell that got inside. It was a bacterium
So in Archaea like the ones in the hot springs in Iceland
Swallowed a cell of that other type of microbial life that was around 2 billion years ago
Bacteria
So what what did that mean for evolution? Well what happened as a result of that is
Complex life evolved
very soon after that event
plants are released algae Green algae leading to plants fungi mushrooms and so on
Animals all diverged quite quickly very very early on quite soon after this cell got within the cell
But why did this moment of one cell consuming another kickstart Complex life?
the answer boils down to one word: energy
The Bacteria that got swallowed evolved into a kind of power station that fueled the whole cell they're called
Mitochondria
The hosts now had the means to get bigger and bigger and maintain bigger genomes
Suddenly cells like the ones we are made of became a possibility
I think that was the critical moment in all of evolution as as we see it because if we're interested in
Intelligent beings or life as we know it then it's really that event is the very beginning of it all