This
appeared a day or so ago! It is a reminder of just how ancient and diverse we
are “down under”!
Where did we come from? Try looking in Shark Bay, Western Australia
Searching for the answers to life’s big questions can take
you to some amazing places on Earth – such as the remote beaches of Western
Australia where clues are found beneath the surface.
ZOE KEAN
Updated 9:04AM November 28, 2024
Do you ever stop and question why and how we have evolved to
be the way we are? Survival is important to us, so why are we willing to risk
our lives for those we care about? In a world where some species reproduce
without sex, why do we need to find a partner to reproduce? Why do we fall in
love, and is there a purpose in pleasure? Why are there males and females? Is
life really that binary? Why do we get cancer? Why do we age, get drunk – even
though it’s bad for us – or spend a third of our lives asleep? And why did we
evolve consciousness and develop rich inner lives?
In contemplating evolution, we see the astonishing
adaptability and persistence of life. Life on Earth has survived meteorite
strikes, ice ages and continent-wide volcanic events. We, and the living forms
we share this planet with, are the direct descendants of the survivors of those
cataclysms. How has this history shaped us? Can learning about these feats of
adaptation help us to live a better life? It’s these questions that have
brought me to Gutharragudu/Shark Bay in Western Australia, a place where red
desert sand meets the sea.
I’m starting my investigation at Gutharragudu because some
of the secrets of the beginnings of life are held by creatures quietly
photosynthesising just offshore.
I flew here on a small regional plane from Perth, having
already crossed the continent from my home in lutruwita/Tasmania. When we
commenced our bumpy descent and burst through the bulbous grey clouds, the
vast glittering bay revealed itself – a shining patchwork of luminous blue
streaked with dark patches of seagrass meadows waving below the water. In
the local Malgana language, Gutharragudu means “two waters”, which describes
how the 23,000-square-kilometre bay is split down the middle by the red dunes
of the Francois Peron Peninsula. The light colour of the water is the first
clue that Gutharragudu is special.
The water in the bay is not deep, and this is particularly
true in an ultra-shallow pocket called Hamelin Pool. The shape of the bay,
combined with a sediment wall caused by the seagrass, means that water flows
into the pool at a higher rate than it flows out. The beating heat of Western
Australia’s sunny days causes the trapped water to evaporate fast. These
factors combine to make the massive pool, which is 1270km sq, almost twice
as salty as the ocean. Hypersalinity is bad news for most species. In this unique
environment, only the most salt-tolerant make it. The extreme conditions have
allowed ancient forms of life, rare in our current world, to survive and
thrive, providing a glimpse into what life on Earth may have been like billions
of years ago.
Cyanobacteria exist in much of the ocean but are greedily
gobbled up by sea snails, so they never get the chance to accumulate. But
snails cannot hack the salinity of Hamelin Pool, which gives these tiny
single-cell organisms the opportunity to collectively achieve something
incredible – to build stone structures that can grow to over a metre tall.
These are called microbialites. Microbialites have different
names depending on exactly how they are formed – they might be known as
thrombolites or stromatolites. Both are found at Hamelin Pool, but here they’re
generally called stromatolites. These rare creations are found in only a few
places in the world outside of Western Australia, including a reef in the
Bahamas and on the bottom of some Antarctic lakes.
The stromatolites’ domain stretches for kilometres, creating
uncanny reefs along Hamelin Pool’s remote beaches. Access is strictly limited;
if you want to swim among them, you need to go with a trained guide. “I usually
take astronauts and astronomers out here,” explains our guide, Luke, as a small
group of us travels over the red dirt track towards the beach. If life is ever
found on other planets, quite likely it would look like these stromatolites.
The sun is out as we drive from red desert to the glaringly
white beach. Hopping barefooted out of the four-wheel-drive, I’m surprised by
the crunch between my toes. My feet are met not by sand but countless
fingernail-sized seashells, metres deep. The cockle (Fragum erugatum) is
another species that is adapted to the salty pool and has multiplied in its
billions, creating long stretches of brilliant white coastline. As I look into
the water, caramel brown shapes are visible in the teal shallows. Are they the
stroms? Yes! With a rush of excitement I realise that I am about to get an
insight into what life was like on the ancient Earth.
Luke shows us the narrow way by which we can wade in without
accidentally touching any of these strange forms. Once I’m knee-deep, I launch
in, float on the surface for a moment and then start gently kicking. Within
seconds a group of stromatolites reveals itself, the choppy water causing sand
to swish around them like structures in a snow globe.
Stromatolites are about half a metre tall with bulbous tops,
dimpled, and an odd grey-cream colour.
Further out to sea the stromatolites become smaller and
flatter, forming mosaic-like patterns on the sea floor.
They are about half a metre tall with bulbous tops, dimpled,
and an odd grey-cream colour. I bob above them, oddly buoyant in the
hypersaline water. The local Malgana people regard the stromatolites as their
Old People and, as I swim on, they remind me of a phalanx of stony warriors.
Further out, the water clears and their shapes change, becoming smaller and
flatter and forming mosaic-like patterns on the sea floor.
Each form could be thousands of years old. Geologist Erica
Suosaari of the Smithsonian Natural History Museum has a long record of
researching Western Australia’s stromatolites.
Later, she tells me over Zoom that tiny bacteria created
these stone structures in two ways. One is by “trapping and binding” sediments,
like sand, that happen to wash past, creating a concrete-like substance. But
they also “precipitate” minerals from the seawater, undissolving them from the
water to create limestone. Coral also uses seawater to create its stone
skeletons. This means only the outer layer of the stromatolites is alive.
Some of the first life on Earth looked exactly like this. If
I’d flown further north and inland, I would have arrived at an arid part of
Western Australia, confusingly called North Pole, where 3.4 billion-year-old
stromatolite fossils have been found. Considering the Earth is about
4.5 billion years old, these are truly ancient.
Are the organisms building the living monuments I’m swimming
over anything like the tiny cells that built North Pole’s precious relics? I
put this to Suosaari and she explains that for many of the ancient fossils,
nailing down exactly what kind of single-celled critter made them is
challenging, so we can only learn about the processes these living things used
to build their monuments. At Hamelin Pool, she says the stromatolites are built
in a way that is “very analogous to ancient structures … regardless of the
species, it’s a process that’s been happening for billions of years and it’s
incredible”. It is possible the earliest stromatolites were made by cells
called archaea – simple cells that are subtly different to the bacteria that
were foundational for the evolution of complex life.
The dominant species at Hamelin Pool, a photosynthetic
cyanobacteria called Entophysalis, is ancient. Evidence of it stretches
back at least 1.8 billion years. Entophysalis is not present in the
world’s other large stromatolite system in the Bahamas, and for Suosaari this
makes Hamelin Pool “the most incredible place on the planet because you really
do have this window into the ancient”.
For at least 80 per cent of the history of life on Earth,
stromatolites were the most common way life presented itself – microbes were
the only game in town. But then things changed.
However, here in Gutharragudu they live on, emerging out of
the millions of Fragum cockles on the sea floor. A range of small
unassuming silver fish, adapted to the extreme salinity of the water, dart
around them. Less common are the baby-blue jellyfish and the languid metre-long
sea snakes that contain enough venom to kill dozens of people. One olive-green
snake takes a break from hunting to headbutt my camera and playfully swim
through my hair before ribboning off, leaving me equally awestruck and frozen
with fear.
As I snorkel through this alien scene set in crystal blue,
I’m struck by the unlikeliness of it all. For much of Earth’s history, life
existed in these relatively simple forms. But from them, and over millions of
years, endless forms – most beautiful and most wonderful – have evolved.
The code to life
I don’t look much like a cyanobacteria – for one, you don’t
need a microscope to see me. But deep in our cells we have a lot in common.
Both of us are built using information stored as DNA. To get to grips with how
life on Earth evolves, we need to get into the nitty-gritty of deoxyribonucleic
acid, DNA to its friends. The broad strokes of evolutionary theory were
understood decades before we knew about DNA. DNA provides the instructions from
which our bodies are made. Molecules called nucleic acids link together in a
chain, creating mega-long complex molecules. The
order of these molecules provides the information needed to create an organism
– our genome.
Nucleic acids preceded life as we know it. They were most
likely cooked up in a hotbed of chemical reactions in ancient Earth’s numerous
mineral-rich volcanic pools, though some scientists believe this happened in
deep-sea vents, or even that the ingredients for life arrived on Earth via an
asteroid.
Either way, early Earth was a laboratory, hosting chemical
reaction after chemical reaction until one day everything came together to form
a cell. While this may have happened more than once, only one lineage had what
it took to survive. This cell is named the last universal common ancestor or
LUCA.
From LUCA, everything that has ever lived evolved. From the
ancient stromatolites of Western Australia to dinosaurs, deep-sea worms and
humans, we are all related to LUCA.
This is an edited extract from Why are We Like This? by
Zoe Kean, published by NewSouth Publishing, and out now.
Here is the
link:
https://www.theaustralian.com.au/health/medical/where-did-we-come-from-try-looking-in-shark-bay-western-australia/news-story/004f5dfdd2bcb5196f36654dd467c603
The bottom
line here is that the life found in these waters is the ancestor of all life on
earth and it was from these that all life as we know it evolved.
Wonderful
that we now know our story all the way back and lucky, I suspect, some of our
ancestors are still around to show us where we came from all that long time
ago!
Fantastic
stuff that partly compensates for all the horror in the world at present….
David.
