Primates are thought to have evolved alongside other placental mammals after the K-T extinction event. They would continue to divide into numerous species over the next several million years.
Around 30 million years ago monkeys had prehensile tails and eyes on the front of their head. Most are thought to have lived in Africa with some migrating to South America, possibly on a raft of vegetation. Five million years later primates would split into apes and monkeys, apes being notable for a lack of a tail.
These early primates spent a great deal of time living in trees, giving rise to hands and fingers to help grip onto the branches. It is thought that this lifestyle also lead to sight being the dominant sense in primates as opposed to smell as in other mammals. It is easy to see that better eyesight would have given a significant advantage when swinging through the trees. Shoulders in apes had a great deal of freedom of movement, as well as other adaptations such as wrists, a wide flat ribcage and shoulder blades on the back. Around seven million years ago the descendants of humans split from those of chimpanzees.
After a further four and a half million years of evolution the first species of the Homo family appeared, Homo habilis. Alongside homo habilis lived homo erectus, which would go on to evolve into homo sapiens. Around 700,000 years ago the last common ancestor of homo sapiens and the neanderthals was alive. The two species would remain separate but lived alongside each other for thousands of years until the neanderthals became extinct.
With the arrival of homo sapiens 250,000 years ago the planet would undergo extensive changes. The key factor that allowed humans to go on and dominate in the manner that they have is due to the large brain and greater mental capacity than other animals. Humans would discover the use of tools and language, therefore reaching a level of communication and cooperation far beyond other apes. The hands that had evolved to climb in trees would prove invaluable in creating tools and later art and writing. The use of tools would allow humans to hunt for meat as well as fish, and language and arts would lead to complex social groups eventually culminating in civilisation. Early tools were made from flint and stone, but later development would see tools made from bones and fragments of antlers.
At around 40-50,000 years ago humans would undergo rapid changes known as The Great Leap Forward. During this time finely made tools, fishing, trading, jewelry, art, music, games and burial of the dead were all developed. This time would also see the expansion of the human population out of Africa and into Europe, Asia and Australia. 12,000 years ago at the end of the most recent Ice Age humans had colonised much of the planet. As the ice receded human populations would continue to grow.
The next key to human development was the arrival of agriculture. While arising at different times in different areas it is thought to have first started around 10,000 years ago in the Middle East. By 2700 BCE agriculture had spread to India, Egypt, China and Mesoamerica. Irrigation, growth of crops and domestication of animals gave humans an early control over their surroundings. Religion also started appearing during this time.
With the advent of agriculture humans could start to move away from their typical nomadic lifestyles. Previously organised into loose tribes the new technology would encourage larger groups to gather and for permanent settlements to start. This would eventually lead to the first civilisations and the start of modern times.
The extinction of the dinosaurs and the end of the Cretaceous period saw the start of the Tertiary period. This time leads right up until around 1.8 million years ago and the evolution of humans. The Tertiary is split into two main eras, the Paleogene and the Neogene, both of which are split into smaller time periods. These times would see the evolution and eventual domination of mammals, birds and insects as life re-evolved to fill the niches left by the departure of the dinosaurs.
Over the 42 million years of the Paleogene the Earth would change considerably. Continents continued to drift away from each other and into their current positions. Laurasia was still in one piece initially but Gondwanaland was splitting into what would become Africa, South America, Antarctica and Australia. India would eventually collide with Asia and form the Himalayas. After eight million years Laurasia was starting to break up into Europe, Greenland and North America.
It took just ten million years from the extinction of the dinosaurs for mammals to take over and evolve into larger herbivorous and carnivorous forms. The first mammals are considered quite primitive, with much smaller brain to body mass ratios than mammals that would appear later on. Little is known about them as remains are hard to come by, some are only identifiable from teeth fossils. By this point many of the main groups of mammals had their own evolutionary offshoots; platypus’, marsupials, the now-extinct multituberculates and placentals were all abundant. However true modern mammals would not evolve until later, in the Eocene era around 55 million years ago.
By the middle stages of the Paleogene mammals had continued to evolve, with hooved animals, rodents, primates, bats and marsupials all present. By this point in time mammals had also taken to the seas. Animals such as Basilosaurus and Prorastomus would be early precursors to whales and seals.
The few reptiles that survived would go on to form modern turtles, crocodiles and pythons. The reptiles would never prove to be as dominant as they were in the Jurassic and the Cretaceous but adapted fairly well to the cooling Earth.
Flowing plants and grasses would come to dominate the plant world, with deciduous trees overtaking the tropical forests of before. Towards the end of the Paleogene era in the Oligocene legumes, ferns, roses, beech and pine trees had all evolved.
Birds continued to evolve and thrive in the new conditions. After the complete extinction of the Pterosaurs the birds had the skies to themselves and diversified into a great number of species. Cranes, hawks, pelicans, herons, owls, ducks, pigeons and woodpeckers all evolved during this time. Some of the most striking birds of the time are ones that have been dubbed ‘Terror Birds’. Flightless birds standing up to three metres tall and running at speeds of up to 30mph, birds such as Gastornis were the dominant predators in their ecosystems. These giant birds would struggle with the arrival of larger carnivorous mammals, and would eventually become extinct as they were no longer able to compete.
With mammals now dominating the planet, primates would continue to evolve and grow into new species. Over time one species of great ape would emerge as the dominant species on the planet, with its brain capabilities far outstripping any other organism before and since.
Once photosynthesising cells present in the oceans had produced enough oxygen to form the ozone layer conditions on land were much more favourable to life than before. Without exposure to ultraviolet radiation cells were much more likely to survive being washed ashore. After a major extinction event 488 million years ago plants and fungi started to grow in out and around the water. Genetic mutation and evolution would see life adapt to the new environment and go on to thrive. Arthropods are believed to be the first animals to appear on land, around 450 million years ago. These early creatures would have been able to feed from the new plants that were growing on land, albeit around the water’s edge.
440 million years ago there was another mass extinction that would kick start evolution. Extinctions are perhaps naively thought of as bad for life, being that most of it is killed off. While it is bad for the organisms alive at the time for obvious reasons, a mass extinction actually has a major benefit for evolution in the path to intelligent life. Every mass extinction to date has been followed by a surge in new species and evolution. The reason for this is that evolution can get into a rut relatively easily, without a mass extinction it is likely that life would stay the same with little adaptation. Extinctions force adaptations and so accelerate evolution.
The result of the extinction event at the end of the Ordovician period, around 440 million years ago, was fish evolving into land-dwelling tetrapods. As their fins evolved into limbs they adapted to breathing air and eventually would live their entire life on land, only returning to water to lay eggs. These animals were the first amphibians and are essentially the genesis of much of life as we know it. During this period plants would evolve seeds and would spread across land, sparking the full colonisation of land by life. In another 20 million years animals would have evolved the capability to lay amniotic eggs as well as having diverged into many distinct evolutionary paths. Insects, reptiles, fish and bacteria were all present at this point.
The next major event has become known as the Great Dying. The Permian-Triassic extinction event is the most severe in Earth’s history. It is estimated that around 96% of marine life and 70% of land dwelling vertebrates would die out. It is also the only known mass extinction of insects. The causes for this are thought to be numerous, including environmental change and a catastrophic event such as increased volcanism or meteorite impacts.
The result of this extinction event was the Triassic period and the start of the age of the dinosaurs. Extending from 251 million years ago until around 199 million years ago the Triassic age is bookmarked by two mass extinctions. During this time the first dinosaurs evolved and it is believed the first mammals, flying vertebrates and flowing plants evolved as well.
The most common land vertebrate during the early Triassic was the Lystrosaurus. It was a small reptilian herbivore about the size of a pig. It had a horny beak and tusks and accounted for 95% of the population of organisms at the time. The Lystrosaurus is notable for being the only species to dominate the planet in such a great number. It is thought that by surviving the Permian-Triassic extinction that they became free of predators and could reproduce with little resistance.
Seeding plants, conifers and cycads would go on to dominate and flourish in the plant world. This would lead to greater insect numbers and would allow greater biodiversity among vertebrates. Towards the end of the Triassic early dinosaurs had evolved along with pterosaurs in the skies and icthyosaurs in the oceans.
As dinosaurs grew in numbers they would force mammalian ancestors to live nocturnally on a diet of insects. It is thought that living in this way would lead mammals to evolve fur and their higher metabolic rates required to function in the cooler night time temperatures.
The Triassic period came to a close 199 million years ago during the Triassic-Jurassic extinction event. During this time around half the species on Earth died out, leaving vast ecological niches. These niches were quickly filled and gave rise to the domination of dinosaurs. The next two periods of time, the Jurassic and Cretaceous, would be inhabited by some of the largest animals that have ever lived and would set in motion the events that would lead to the evolution of modern mammals.
In the scientific community there are two main schools of thought on the origin of life on Earth. One is that life was started here via a process known as panspermia. This is where bacteria are carried through space from another planet on a comet or meteor. The idea is that these bacteria would somehow survive impact and then go on to flourish on the new planet, in this case Earth.
While the theory of panspermia is certainly valid, Earth was heavily bombarded by meteorites prior to the start of life, it still doesn’t answer how life came to be in the first place. The likelihood of something surviving an impact combined with landing somewhere where it could thrive seems like a remotely small chance as well. The more widely accepted theory is that life on Earth originated here and did not come from another planet.
No concrete theory has been put forward that shows how life can come into being from non-living material yet. Without perfectly sterile lab conditions and a few hundred million years it may prove impossible. However it is theorised that life began as a series of organic chemicals and molecules. One of these molecules gained the ability to replicate itself. The crucial feature of this replication is that it was not perfect, there would sometimes be ‘errors’ in the reproduction.
If an ‘error’ in reproduction left that particular strand at a disadvantage then they would not reproduce as much and would eventually die out. If an error or mutation left a strand at a clear advantage, however, then they would reproduce in greater numbers and would take over. This is the start of natural selection and evolution, the theory that is thought to govern the development of all life right from the beginning to where we are today. Eventually DNA would emerge as the dominant force in replication and life was well on its way to becoming cellular.
Eventually primitive life would evolve membranes and so cells were born. The leap to membranes is actually easier to comprehend as the phospholipids present in cell membranes form bilayers spontaneously when placed in water. This property would allow the contents of life to be contained within the confines of a cell. The cells that would go on to become the ancestors of all life on Earth were present at this time, just over 3.5 billion years ago. They were primitive compared to modern cells, still lacking a nucleus, mitichondria and chloroplasts.
The next main development that would change the planet came with the advent of photosynthesis. Photosynthesis would allow life to use sunlight as an energy source. Cells that did not develop photosynthesis would also benefit as they could consume the photosynthesising cells. The secondary effect of stimulating the growth of life was what is know as the ‘Oxygen Catastrophe’. Oxygen is a waste product of photosynthesis and was toxic to a great many organisms. The waste oxygen would have first become bound to limestone and iron in the sea, before it could escape into the atmosphere. The atmosphere would slowly build up in concentration of oxygen and the ozone layer eventually formed, guarding the planet’s surface from harmful ultraviolet radiation. As a substantial amount of life died from oxygen some would find a way to harness it to enhance their metabolism.
Cells would continue to adapt over millions of years, gaining organelles and nuclei. At this point in history, around 1.1 billion years ago, the first supercontinent was beginning to take shape and plant, animal and fungus cells had split and were clearly defined, although still single-celled. As colonies of cells built up in volume over time some cells in certain parts of the colony would evolve into specialist cells giving a benefit for the whole colony. As this division began to take place it could be said that this was the start of multicellular organisms. Around 900 million years ago the first multi-celled animals began to appear.
Around 770 million years ago scientists believe that the planet went through a phase that has become known as Snowball Earth. For 20 million years the oceans froze over and the Earth entered a severe ice age. Eventually after time volcanic eruptions would cause enough carbon dioxide to enter the atmosphere and heat the planet due to the greenhouse effect.
By 530 million years ago fish had evolved and were the first known vertebrates. With the ice melted, the ozone layer present and complex life thriving in the ocean it would only be a matter of time before life would take to land.
Fourty-five percent of the American population believe that God created humans and placed them on the Earth less than 10,000 years ago. It is an incredible statistic. That’s 135,512,978 people in the USA who believe the Earth is 10,000 years old, twice the population of the UK.
The question of faith has always been a contentious, and interesting one. Causing more wars than anything else in history, religion has certainly been one of the more interesting phenomena that humanity has created for itself. The dominating religion in the Western world is Christianity and it is certainly hard to get away from it.
As scientific thinking and theories have improved over the last couple of hundred years there have been those religious fanatics who have chosen to reject reasonable ideas and logical thinking and cling to their spiritual beliefs in the wake of overwhelming evidence to the contrary.
What got me thinking about religion and it’s conflict with science was a particular branch of Christianity; Creationism. Creationism is the belief that evolution is a myth and that everything was created by an intelligent designer. In this case the designer is God. Strangely it isn’t actually the theory of intelligent design that irks me here, I like to think I’m fairly open to new ideas and generally accepting of religious beliefs, even if I do not agree with them. What does bother me is how the creationists present their views, and how they have such a large population completely brainwashed into the belief.
The creationist argument is that life and the universe as we understand it is so complex, infinitely so, that for it to have happened by chance is ridiculous. They believe that the Earth and all the life that lives on it has been designed and placed there by a divine creator, a God. Obviously this flies in the face of evolution, the theory with millions of years worth of hard evidence.
A common theory put forward by well known creationists is that the banana presents the ‘atheist’s nightmare’. They say that the banana is perfectly suited for a human hand, is colour coordinated to show how ripe it is, has a bio-degradable wrapper, is good to eat and is perfectly shaped for the human mouth. They say that with all these things taken into account it is so obvious that the banana has been designed for humans to eat and hasn’t just occurred by chance. What they fail to mention however, is that the wild banana is quite different. Filled with hard black seeds it is completely inedible. The banana that we know has been genetically modified over thousands of years into it’s current form. In fact the designer of the banana is Man himself, hardly proof of a divine creator.
They then go on to compare various man made structures to naturally occurring phenomenon. They say that to say a building has no designer is ridiculous, and so therefore it is also ridiculous to say that nature has no designer. What they fail to mention is that everything that is naturally occurring has had millions, or billions of years to evolve and come into being. To say that an eye has naturally evolved does initially seem far fetched, but when it is backed up with billions of years of chance it suddenly doesn’t seem so hard to believe.
Imagine playing the lottery every day for five billion years. You’d win quite a few times wouldn’t you? Well this is how evolution works. Over such massive time frames tiny chances of things happening become almost certain to happen. I would guess that religious believers have difficulty in comprehending the vast amount of time that existed before Man. The problem with religion and creationism is that everything is so centered around our own species when really we’ve only been around for an astronomical blink of an eye. Even in our own planet’s history we are quite insignificant, we’ve been around for 200,000 years as opposed to the 500 million years that fish have existed for. To say that a God has designed everything just for us seems entirely implausible to me.
Of course one could never be 100 percent sure that there was no God. You could never say that without having absolute knowledge of everything that exists, has existed or will exist. In this regard I am open to the fact that a God may exist, although I do not believe that one does.
I think that fabricating beliefs based on an old book and presenting them as fact is wrong, however. Surely science and rational thinking should be the basis on which opinion is formed. The purpose of science is to find evidence and present theories based on it. By turning yourself over to a religion you are able to just explain everything away with ‘God did it’. Against such an point of view it becomes difficult to construct an argument. Inevitably they will ask some questions that science does not have an answer for yet, and then they can answer it with ‘God did it’. Science does not pretend to have answers for things it does not understand yet, but preset facts based on real evidence and testing.
Organised religion and faith are relics from the past, unneeded in today’s society. They were used to govern primitive people and give answers to things that people could not understand yet. Essentially ruling people with the fear of going to Hell, religion is no longer needed now that we have organised rules and police forces. By perpetuating the falsehood of creationism and presenting religion as fact these people are slowing the scientific advancement and development of our species.
Religious evangelism needs to accept science or cease spreading its lies, for the good of everyone.
