Before the 1950's if evidence had been found of organic molecules such as amino acids (the building blocks for proteins) on another planet, they would be taken as a sign of life. Stanley Miller changed that. In 1953 he did an experiment where he reproduced what was thought to be the 'primeval soup' and sent electricity through it. He created 3 amino acids. Nature uses 20, and it wasn't until years later that John Oro and Melvin Calvin created the other 17 plus the 4 nucleotides that are used in DNA plus fats and sugars. It had been shown that they can all be created without life.

This of course is not life, just some of its constituents, so how did life start? There are many theories about where it started. It may have been in a shallow lagoon or a puddle at the bottom of a volcano or in the deep sea by one of the deep sea vents. We may never know, but the idea behind these theories is this, that a long organic molecule was formed that could make a template of itself. This is not a difficult thing to do, and some have been reproduced in the laboratory. This was not DNA, it was probably not a long chain, but once just one molecule in a thick soup of organic molecules could replicate the move towards life had begun. This molecule would make copies of itself, and these would make copies in their turn. Nothing is perfect, however and errors would be made. This introduces variation into the molecules, some would replicate faster than others, and so these would spread quicker through the molecules. The quality of the copies of these molecules would be much poorer than for the robust DNA and there would be a lot of variation. Some templates produced will not have been accurate enough to make copies, but may have had other effects, such as producing an insoluble molecule which could for a barrier around the replicating molecule (these have been recreated in the laboratory, known as coccoids and microspheres, which are semi-permeable. These have also been found in rocks over 3 billion years old). Other inaccurate copies may have had the effect of breaking up less robust replicators.

With a microsphere and other active molecules, this is the basis of a simple bacteria, a prokaryote. The first evidence for these is found in rocks 3.7 billion years old. There would still be variation, replicators that produced more efficient barriers would last longer and so form copies of itself that had the same characteristics. A replicator that could break up others better would survive better, until a replicator came along, tougher than anything before it. DNA. This process would have taken millions of years and many steps (RNA probably came first), but once a molecule as stable as DNA was around, nothing could compete. Simple molecules for using sunlight for energy appeared, nothing like photosynthesis, but with variation (and survival of the bags of molecules that worked best) something approaching photosynthesis would have happened (the first evidence of photosynthesis appeared 3.4 billion years ago) , and with increasing variation better and more efficient photosynthesis would result (the well known version of photosynthesis appeared 2.4 billion years ago).

Of course the waste product of photosynthesis is a chemical so destructive it can destroy cells. It is a chemical that releases free radicals which react violently with almost anything, and that cause many cancers today. That chemical is oxygen.

The first free oxygen that was available went into oxidising the iron ions diluted in the ocean. This didn't take all the oxygen, and, with the variation between very oxygen intolerant to slightly tolerant, in some environments oxygen tolerance would have become the norm. The incredible energy availability that oxygen induces would not have been left untapped for long, and prokaryotes that could use oxygen would have flourished with the abundance of energy. To other prokaryotes, though, oxygen was poisonous, and at some point an oxygen metabolising prokaryote was used by an oxygen intolerant one to provide it with energy. This became the most intimate symbiotic relationship possible, with the oxygen using bacteria being encapsulated into the other. Leading to a more complex cell, known as a eukaryote. These could grow larger due to the increased energy. Other smaller bacteria were subsumed into these cells, and two different types of eukaryotes began to emerge. One with only oxygen using prokaryotes (now known as mitochondria) in it, and another with a different type of prokaryote in addition. These could photosynthesise, and are now known as chloroplasts. The difference between animals and plants had emerged.

There is an excellent snapshot of what life was like 570 million years ago. It was found in British Columbia and is known as the Burgess Shales. There has been found in that deposit some extraordinary creatures, experiments in invertebrate body forms, but amongst them has been found a small animal known as Pikaia. It has a simple line of nerves running along it. The first backbone, maybe. It also has the muscle segments of a fish. From this or other animals like it, the first vertebrates evolved. The first fishes had no jaws, and were known as agnathans. An example of this is the 465 million year old arandaspis. The first jawed fish (placoderms) evolved about 438-365 million years ago. The first fish, of which sharks and rays are the descendants have cartilage making there bones and are known as chindricthyians. Sharks and rays also do not have a swim bladder, which is a sack of air which bony fish (ostiecthyans) do possess. This was a critical development for fish, allowing them to control their own buoyancy. One very successful group of fish at this time were the lobe finned fishes (osteolepid). These had strong fins, with which they could pull themselves along the sea floor. It is believed that it is from these fish that land vertebrates first evolved. These lobe finned fish had another advance that helped them in the stagnant waters that they lived in. They had lungs. The swim bladders were used as a new method of taking in air instead of their gills. It is not known why these fish moved onto land, one theory is that when the seas retreated (the climate became drier about this time) they had to spend longer and longer on land looking for new places to live, but it is considered more likely that they found an untapped food source that they could take advantage of, namely the insects that now lived on land. Plants, insects, spiders and millipedes had moved onto land about 438-408 million years ago. The best guess from many candidates for the actual fish amphibians evolved from is Eusthenopteron. This was a lobe-finned fish with lungs, and what is important to vertebrate development, the nasal passage connects to the roof of the mouth in the same way that land vertebrates do, and a way which is rare in fish. 370 million years ago we have the first remains of amphibians, like Ichthyostega. This is an animal that has the reinforced bones and ribs necessary to prolonged life on land, and it has a real neck separating the skull from the shoulders, but it is streamlined exactly like a fish and it has a fish-like tail. The evolution of the amphibians then continued, turning them to look more and more like land living animals, but, as is evident from frogs, newts and salamanders today, they never could make the break and become full landlubbers.

One group of amphibians did make that break. The main thing that ties an amphibian to the water is the eggs that it lays do not have a waterproof shell, and so will dry out. Reptiles developed a shell that was waterproof, but still allowed gaseous exchange. These eggs also contain a food supply or amniotic sac, and so all the animals that developed from reptiles are known as amniotes. The first reptilian animals were around about 350 Million years ago, but this is known only from their body shape and characteristics, no eggs from that time have been found.

Reptiles were very successful they diversified very quickly. Fossil reptiles can be identified by the number of holes in the side of the skull. These holes are called temporal fenestre. There were three main groups of reptiles, anapsids (none), Diapsids (two temporal fenestre) and synapsids (joined).

The most successful reptiles were the diapsids. They evolved into dinosaurs. Dinosaurs had the advantage over other reptiles in that there legs went straight down from their bodies, like a horses, instead of out to the side first like the crocodiles. This is a much more efficient method of moving giving them dominance over the land for over 100 million years.

One group of dinosaurs developed a form of insulation to help them stay warm. These were the dromaeosaurs, the scientific name of the velociraptors of Jurassic Park fame. Dromaeosaurs have been found with these insulating structures, known as feathers, recently. A Times report of 24^th June 1998 told of their discovery in China. The feathers are not the asymmetric flight feathers of birds, but are like the downy feathers that birds use as insulation to this day. These were the first birds, and now they are the only descendants of the dinosaurs alive.

One group of synapsids developed a different way of controlling their body temperature. They developed fur. They also started feeding their offspring from modified sweat glands. These started producing milk, now the offspring could develop in security without having to search for food. These animals, of course, were mammals. There was another change in their development, they started producing live young, some even went as far as having the whole development of the offspring happening inside the body of the mother. This was a great boost to the child's development, allowing much more energy to be supplied and so much faster and more sophisticated children could be born. The mammals were ready to take over the Earth, but they had to wait until the current rulers died. This happened 65 million years ago at the end of the cretaceous period. Suddenly, the small cretaceous mammals could diversify and all the large animals of today evolved.

Primates evolved in Africa. The most primitive type, the lemurs, rely on smell more than sight. Monkeys started relying on their eyes more than their sense of smell, and this became most developed in the apes. This reliance of sight, and the adaptability of the hand with the opposable thumb has led to an increase in the relative size of the brain, and the apes, such as gorillas and chimpanzee's developing a highly developed social system and chimps actually fashioning tools out of sticks.

A few million years ago, One ape decided to try a different method of caring for its young. It went for a very labour intensive method. This meant that each child would have more chance of survival. This required much more effort on the part of the mother, and she needed to carry the baby around. The father needed to fetch food for his family, and so these apes 'settled down'. To carry more food, the father needed both hands free and so started walking on two legs. These changes happened over a long period of time, and the outcome was an ape know as Australopithecus. The best known example is Lucy, a 46% complete skeleton of a young lady found in Kenya. Foot tracks of these animals moving in a family unit have also been found. This new method of locomotion left the hands free. These apes started using them in similar ways that chimps do today. Using natural objects such as rocks and sticks to help them survive.

This use of the hands led to selection for apes that had bigger brains to use their hands better, which pushed the selection for bigger brains even faster. Tools started to be made. Rocks of flint was struck by other rocks to produce a new tool, that must have been 'seen in the minds eye'. A new species of ape, Homo Habilis took full advantage of this and this animals survival was also assured by the use of another development. The use of fire.

Now, with wild beasts kept at bay and the night no longer as dark, speech began to be developed, this can be seen in the examination of the vertebrae of these early hominids. The backbone to the lungs became wider, allowing more nerves to control much more accurately the way that air was expelled, giving the ability to achieve a level of communication never before heard. The downside of fire was that now that food could be cooked, these animals teeth became softer than before. Another development that archaeology has traced.

Other apes of this lineage evolved, then one came along with the largest brain size in relation to its body than any other animal. Homo Sapiens Neanderthalis. It was a sub-species of these, known as Homo Sapiens Sapiens that became modern man. The development of these two went side by side, until about 50,000 years ago when modern man developed art. The Neanderthals tried to imitate it, but poorly, and declined until their extinction about 32,000 years ago, leaving only one animal of that lineage alive today.

To think of man as the most advanced animal, the pinnacle of evolution is wrong, however. Any animal alive today is the pinnacle of its line of development, and its ancestors, without exception must have been successful. We are just one other line of development that life took.