Before
we understand human beings, we need to understand how we came to be. One of the
most thrilling experience of my life happened in one of the holiest places of
India, Chitrakoot. Legend has it that King Rama, his wife Sita, and brother
Lakshmana spent eleven out of their fourteen years of exile here. My group and
me were also out there for a fourteen-day exile, looking at the outcrops of
Vindhyan. I was standing over the Tirohan Dolomite of the Lower Vindhyan and
staring down at one of the oldest evidence of life. I was looking at our tiny
ancestors- the phosphatized stromatolitic microbialites, a variety of red algae-
that was 1.6 billion years old. They are one of the oldest direct evidence of
life. Isn’t that fascinating? What’s more fascinating is to trace back the
evolution of the complex humans from those tiny creatures.
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| Stromatolites |
The
earliest evidence of life dates back to 3.8 billions years. 3.8 billion years
is too long to preserve direct evidence of micro life. Scientists need to
depend on indirect evidence, which came from the carbon-isotope analysis of
rocks from the Isua and Akilia greenstone belts of southwest Greenland. There
are also structures within the rocks, which according to some geologists, look
like stromatolites. How life started is still a big puzzle that needs to be
solved. Did a creator design it? Was it just a chance episode? Or is it that we
can ask this question because we happen to be in one of the infinite universes
that happen to have the right conditions for life? Was it an obvious outcome of
the initial conditions of our universe? Unfortunately, as things stand now, we
are not going to have an answer anytime soon.
Hungarian
Nobel prizewinner Albert Szent-Györgyi once said, ‘Life is nothing but an electron
looking for a place to rest’. As long as it is ‘looking’, we are good. As long
as the electrons are snatched and transferred from one atom to another, life
will continue. For example there are bacteria’s, which strip electrons from
hydrogen, and attach them into carbon dioxide generating methane and water. All
living things do that. Strip electrons from something and attach them to
something else to tap the energy required to live. Electron transfer was the
first process that happened when life was born, in the primordial soup or
deep-sea hydrothermal vent, or wherever it started. In the process it was
creating information about its own identity.
Miller-Urey
experiment showed that biology could be cooked out of chemistry, given the
right ingredients and a spark. Jeremy England, a biophysicist, thinks that
complex structures like living things can naturally grow from restructuring
effect, which he calls dissipation-driven-adaptation. Atoms try to restructure
themselves in order to burn more and more energy resulting in the rise of
entropy, as required by the second law of thermodynamics. And the most
effective way of doing it is replication. However, the conditions on early
earth or inside a cell are very complex and cannot be predicted from first principles.
All experiments done so far are only speculations. Whichever way life formed,
it was using geochemical energy (water-rock reactions) to survive.
The
next step life required, after it was “created”, was replication of the
information that made the blob of protein. One of the popular theories suggests
that self-replicating nucleic acids were the first replicators, from which RNA
took shape. Recent findings propose that Mars was the best place for these
replicators to form. Martian or not, our tiny ancestors must have been
cannibals. Proteins required eating protein to survive, thus arose the first
predators and their preys. As if creation of replicating proteins was not
enough a miracle, there was an even bigger miracle that made us - endosymbiosis
between two prokaryotes. According to biochemist Nick Lane the miracle of one
bacteria getting inside another and surviving there for generations has helped develop
complex life like us. One such bacterium is the mitochondria living inside our
cells. This triggered a chain of events, including formation of nucleus, sex,
two sexes, predators and preys.
These
early autotrophic forms of life soon turned to heterotrophic by feeding on the
dead cells of others. This suddenly triggered a race of survival between the
predator and the prey, making way for Darwinian evolution where the fittest
gene survived and spread. While the preys developed hard shell or became agile,
the predators developed stronger teeth to crush their prey. Sometime, before
the more complex predator prey evolved, some of these early life forms learned
to utilize the energy from the sun to power life. This is when we find
stromatolites and banded iron formations in different parts of the globe. From
anoxygenic photosynthesis, life learned to take in oxygen by breaking down
water molecules. This aerobic photosynthesis started to increase the oxygen
content in the atmosphere. This resulted in the Great Oxidation Event around
2.2 billion years ago. Red bed outcrops found around the earth are evidence of
this global event. Rise of oxygen created the Ozone layer, making earth more
habitable. Oxygen is the most efficient element in terms of the amount of
energy released per electron transfer, apart from the much less abundant
chlorine and fluorine. This helped in the creating of complex life form.
The
first single celled eukaryote evolved around 1.6 billion years ago. During the
Snowball Earth, that happened 750-600million years ago, oxygen level rose
rapidly to modern day concentrations. Oceans were oxygenated and the earliest
know complex multicellular organisms, called Ediacarans, took birth. Multicellular
organisms developed special systems, like the nervous system, that helped them
perceive the world in a more advanced way. Desires were developed that helped
the organisms to survive and reproduce. After a pause of a century or so since
the first Ediacarans, life began to explode. This period, as recorded in the
fossils of around 541 million years, is known as the Cambrian explosion.
The
best evidence of Cambrian explosion in India is preserved in the Blue City of
Rajasthan. We went to Jodhpur as part of a fieldtrip to look at the rock
outcrops and understand the reservoirs that hosts the largest onland oil
discovery of India. The pink Jodhpur sandstones are too old and too tight to
interest a petroleum geologist, however they would fascinate any geologist.
These famous sandstones have been queried and the slabs sold as building
materials all over the world. While we are loosing these rocks, that have
survived for over 540 million years, rapidly, it also gave us the opportunity
to look at some fresh rock faces. In one of those fresh rock faces were some
weird looking disk-shaped fossils. These discoidal fossils are the most common
and youngest Ediacaran fossils in the world. Since Cambrian, life never looked
back.
The
first dominant vertebrates were the prehistoric fishes that swam the ancient
ocean 500 to 400 million years ago. From these ‘fishes’ evolved the adventurous
tetrapods at around 400-350 million years ago. They were the first animals to
get out of the ocean and colonize the dry lands. For the next 50 million years
the amphibians dominated the land and had the better of the evolving reptiles. But
soon the tables were turned. Reptiles grew big and became the glamorous
dinosaurs, while the amphibians shrunk into frogs and toads. Our tiny furry
warm-blooded ancestors evolved around 230 million years ago. They lived under
the shadows of the mighty dinosaurs. While these first mammals were no matches
for the giant reptiles, they were the masters of hiding, running, and most
importantly, surviving. Our ancestors survived what even the dinosaurs could
not – the K-T extinction. As the reptile menace perished, it was time for the
mammals to flourish. Filial emotions evolved in mammals to help then bind with
each other. Unity was the key to mammal’s survival. Primates evolved from the
tree hugging mammals of the tropical forests. They are the most social of all
animals and the social emotions, like guilt and pride, became a dominant part
of their brain. Strong emotions created a highly sophisticated animal. Who knew
what these innocent looking animals would soon be up to.
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| Primates and emotions |
So
far we saw how apes evolved from the single celled organisms. In this section
we will see how we evolved from apes. It all began more than 30million years
ago, ~200kms below the surface of earth, at a temperature of 1500°C, somewhere
under the Mountain of Moon. That was where a dangerous force was unleashed,
that changed the world forever. The heat, 200kms below the earth (geologists
calls it magma plume), was slowly tearing Africa apart (rifting). The force
that was soon going to change our fate was first changing the geography of East
Africa. The landscape slowly evolved into The Great African Rift Valley. It
created deep lakes like Lake Tanganyika that is 1470m deep, to high mountains
like the 5109m tall Mt. Rwenzori, within next 20 million years. The high
mountains blocked the clouds creating a rain shadow in the eastern part of
Africa making it more arid. A kilometer reduction of topography would
have meant I would not have been here to write this book, the world would have
been lot greener, and no one would have been there to worry about global
warming.
The
single most important thing that separates us from other primates is that we
walk upright. According to the most popular theory the colossal change of
climate initiated by the tectonic forces triggered evolution of apes. The
climate in which our ancestors became so comfortable changed from rainforests
to savannas. These changes meant that the apes themselves had to change to
adapt to the new conditions. One of such change was the decision to walk
upright. The reduction of trees meant that they were forced to come down from
the comfort of the trees into the unsafe land and also had to cover huge areas
for food. What actually influenced bipedalism is debatable, but one thing
is for sure, it gave us an immense advantage. Bipedalism is effective in terms
of energy conservation making us more agile. It not only helped us catch preys
but also helped us run away from the predators. But the most significant aspect
of bipedalism was that it freed our hands. This meant that now we were ready to
go on the offensive. Free hands were the most powerful weapon any animal ever
had. Use of hands made us more intelligent as we used it to create tools
that were useful for survival. We were ready to take our future into our own
hands. Use of tools required hand eye coordination, fine motor skill
development, and process of large volumes of information. It required powerful
brain. Bipedalism happened about 5 million years ago and it corresponds to the
time when human brain began to develop, not just in size but also complexity.
Desires were the first to develop, followed by emotions. Now the third and the
most powerful part of the brain were evolving. This part is call intelligence.
The
next big step our ancestors took was control of fire. The oldest evidence of
control of fire dates back to 1.7 million years, but the definitive evidence of
controlled use of fire dates back 600,000 years ago by Homo erectus. By 125,000 years anatomically modern humans were
masters of controlling fire. Fire gave us big advantage over other animals. It
warmed us at night and helped us spread to colder places. Fire not only helped
us forge better weapons, it also helped us create works of art like terracotta
statues and pottery. Fire helped us scare predators and cook preys. Had we not
been playing with fire, mammoths would probably be still around and we would
probably be still in caves. The cooked food was healthy as it killed unhealthy
bacteria’s like E.Coli and salmonella.
Cooked food was easier to digest. As a consequence our stomach, teeth and mouth
became smaller and there was a decrease is the size of our gastrointestinal
track and organs in the digestive system. Richard Wrangham suggests that the
brains now used this freed up energy, making it bigger and us smarter. Change
in food habit also helped. Increase in meat and shellfish consumption increased
dopamine secretion in the brain making us smarter. The intelligent human beings
had a better chance of survival and finding mates. The genes that preferred
intelligence and bigger brain size rapidly spread in the population by natural
selection.
The
bigger brain did come at a cost. While being just 2% of our body weight, human
brains consume 20% of our energy requirement, much higher than any other
animal. This increased our food requirement, keeping us busy. Had we been a bit
less smart, the world would have a lot more food. There was also less energy to
built muscles. Our intelligence came at the cost of our strength. The large
brains also meant large skull to contain it. This made childbirth difficult and
painful. The birth canal of women grew wider. But it was not enough as the
brain of the primates of ‘homo’ genus continued to grow. The solution was in
giving early birth, before the skull became too big. The need to take care of
infants for a longer period of time bonded the parents together. Emotional part
of the brain helped develop the intelligent part by creating the feeling
‘love’. Partners in love stayed
together and cared for their offspring. The brains could now continue to grow,
but it made these primates beings less mobile. They stayed in one place for a
long time. Females took care of the infants while males went to hunt.
The
biggest invention of the “smart” us was probably language. Language not only
helped in communication, but also in making and sharing stories. It was a
cognitive revolution for our species, which could well have been triggered by
some sort of mutation. Noam Chomky would tell you that language is in our
genes. One must not get carried away here to believe that we are the only
species that communicate using language. We know of birds like parrots that can
make sounds just like us. A whale can communicate meaningful words with another
whale that is 100s of kms away using sonic waves. Green monkeys has different
words to differentiate between ‘Careful! Lion!’ and ‘Careful! Eagle!’ Fellow
monkeys reacts appropriately depending on the warning. Homo sapience, however,
has developed the most complex language amongst all animals, a language that
helps us to gossip. Other animals communicate about immediate danger, while we
can teach dangers of predators to our kids through stories even before they
face a threat. We can talk and plan ahead to save ourselves from predators,
while at the same time strategizing how to kill our next prey. We can gossip
about whom you like and whom you don’t, about who is helpful and who is a
cheater, about who loves whom and who is sleeping with whom. We created
legends, we created myths and above all, we created gods. According to Yuval
Noah Harari, none of them would have been possible without language. This great
revolution probably happened around 70,000 years ago. That was the time when
humans migrated out of Africa (even though some latest research points its
fingers towards Europe), improved our art and craft abilities, and drove
Neanderthals towards extinction. This time, also known as the “Great Leap
Forward”, coincides with climate change resulting from the great Toba eruption.
The deadly eruption created a ten-year-long winter. It resulted in an ecological
disaster that destroyed most of the vegetation. The long and harsh winter
decreased the human population of the world to just 3,000-10,000 individuals.
All human beings alive today are descendants from those small numbers of
individuals, as proven by genetic studies. In fact, every person alive in this
world today can be traced back to a single female who lived 140,000 years ago
and to a single male living 90,000 years ago.
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| Arts and Intelligence went hand in hand |
Once
they were out of the comfort of their ancestral home in Africa, they required
innovation to survive. They took risks and ended up discovering more. These new
adventures were changing their brain. The once apes, were now slowly rising up
the food chain. Homo sapience’s were evolving into a perfect killing machine.
The cave paintings by this early sapience revealed their love for hunting,
music, and dancing. As the ice age melted away and earth became more
hospitable, people started getting organized into groups and settled down in a
fertile land. Human beings started to tweak the rules of nature. In nature, the
big fish eats small fish, and the fittest survive. Humans created a world where
even the weak could survive. They named this world ‘civilization’. In the new
world they were making, unity was strength. Civilization needed a tool—an
idea—to bind people together. The idea came in the form of society and
religion. Some among the clans claimed to be closer to god and declared
themselves priests. Some of these priests specialized in healing the sick, some
in predicting the future, while others at changing it. The first temples
(dolmens) were created out of stones and menhirs. The logos of intelligence and
mythos of emotions was growing together. From the single cells of Isua and
Akilia to a complex organism that can read and write, we have come a long way.
