`star` Origin and Evolution of Lower Life forms
`star` Origin and Evolution of Amphibians and Reptiles
`star` Origin and Evolution of Mammals
`star` Origin and Evolution of Man


● About `color{Brown}"2000 million years"` ago (mya) the `color{Violet}"first cellular forms"` of life appeared on earth.

● The mechanism of how `color{Violet}"non-cellular aggregates"` of giant macromolecules could `color{Violet}"evolve into cells"` with membranous envelop is not known.

● Some of these cells had the ability to `color{Violet}"release"` `O_2`.

● The reaction could have been similar to the `color{Violet}"light reaction in photosynthesis"` where water is split with the help of `color{Violet}"solar energy"` captured and channelised by appropriate `color{Violet}"light harvesting pigments"`.

● Slowly `color{Violet}"single-celled organisms"` became multi-cellular life forms.

● By the time of `color{brown}"500 mya"`, `color{Violet}"invertebrates"` were formed and active.

● `color{Violet}"Jawless fish"` probably evolved around `color{Brown}"350 mya"`.

● `color{Violet}"Sea weeds"` and few plants existed probably around `color{Brown}"320 mya"`.

● We are told that the `color{Violet}"first organisms"` that invaded land were `color{Violet}"plants"`.

● They were `color{Violet}"widespread on land"` when animals invaded land.


`star` `color{Brown}"Amphibians"`

● `color{Violet}"Fish with stout"` and `color{Violet}"strong fins"` could move on land and go back to water. This was about `color{Brown}"350 mya"`.

● In 1938, a fish caught in `color{Violet}"South Africa"` happened to be a `color{Violet}"Coelacanth"` which was thought to be extinct.

● These animals called `color{Brown}"lobefins"` evolved into the first amphibians that lived on both land and water.

● There are `color{Violet}"no specimens"` of these left with us.

● However, these were `color{Violet}"ancestors"` of modern day `color{Violet}"frogs and salamanders"`.

`star` `color{Brown}"Reptiles"`

● The amphibians evolved into `color{Violet}"reptiles"`.

● They lay `color{Violet}"thick shelled eggs"` which do not `color{Violet}"dry up in sun"` unlike those of amphibians.

● Again we only see their `color{Violet}"modern day"` descendents, the `color{Violet}"turtles, tortoises"` and `color{Violet}"crocodiles"`.

● In the next `color{Violet}"200 millions years"` or so, reptiles of different `color{Violet}"shapes and sizes"` dominated on earth.

● Giant ferns (`color{Violet}"pteridophytes"`) were present but they all fell to form `color{Violet}"coal deposits"` slowly.

● Some of these land `color{Violet}"reptiles"` went `color{Violet}"back into water"` to evolve into `color{Violet}"fish like reptiles"` probably `color{Brown}"200 mya"` (e.g. `color{Violet}"Ichthyosaurs"`).

● The `color{Violet}"land reptiles"` were, of course, the `color{Violet}"dinosaurs"`.

● The biggest of them, i.e., `color{Violet}"Tyrannosaurus rex"` was about `color{Violet}"20 feet in height"` and had huge fearsome dagger like teeth.

● About `color{Brown}"65 mya"`, the `color{Violet}"dinosaurs suddenly disappeared"` from the earth. We do not know the true reason.

● Some say `color{Violet}"climatic changes"` killed them. Some say most of them `color{Violet}"evolved into birds"`. The truth may live in between. `color{Violet}"Small sized reptiles"` of that era still exist today.


● The `color{Violet}"first mammals"` were like `color{Violet}"shrews"`.

● Their fossils are `color{Violet}"small sized"`.

● Mammals were `color{Violet}"viviparous"` and protected their `color{Violet}"unborn young"` `color{Violet}"inside the mother’s body"`.

● Mammals were `color{Violet}"more intelligent"` in `color{Violet}"sensing and avoiding danger"` at least.

● When reptiles came down `color{Violet}"mammals took over"` this earth.

● There were in `color{Violet}"South America mammals"` resembling horse, hippopotamus, bear, rabbit, etc.

`star` `color{Brown}"Effect of Continental Drift"`

● Due to `color{Violet}"continental drift"`, when South America joined North America, these animals were `color{Violet}"overridden"` by `color{Violet}"North American fauna"`.

● Due to the same continental drift `color{Violet}"pouched mammals of Australia"` survived because of `color{Violet}"lack of competition"` from any other mammal.

● Lest we forget, some `color{Violet}"mammals"` live `color{Violet}"wholly in water"`.

● `color{Violet}"Whales"`, `color{Violet}"dolphins"`, `color{Violet}"seals and sea cows"` are some examples.

● Evolution of `color{Violet}"horse"`, `color{Violet}"elephant"`, `color{Violet}"dog"`, etc., are special stories of evolution.

● The most successful story is the `color{Violet}"evolution of man"` with `color{Violet}"language skills"` and `color{Violet}"self-consciousness"`.


`star` `color{Brown}"Dryopithecus and Ramapithecus"`

● About `color{brown}"15 mya"`, primates called `color{violet}"Dryopithecus"'` and `color{violet}"Ramapithecus"` were existing.

● They were `color{violet}"hairy"` and walked like `color{violet}"and chimpanzees"`.

● Ramapithecus was more `color{violet}"man-like"` while Dryopithecus was `color{violet}"more ape-like"`.

`star` `color{Brown}"Australopithecines"`

● Few fossils of `color{violet}"man-like bones"` have been discovered in `color{violet}"Ethiopia and Tanzania"`.

● These revealed `color{violet}"hominid features"` leading to the belief that about `color{Brown}"3-4 mya"`, `color{violet}"man-like primates"` walked in eastern Africa.

● They were probably `color{violet}"not taller than 4 feet"` but walked `color{violet}"up right"`.

● `color{Brown}"Two mya"`, `color{violet}"Australopithecines"` probably lived in `color{violet}"East African grasslands"`.

● Evidence shows they `color{violet}"hunted with stone"` weapons but essentially `color{violet}"ate fruit"`.

`star` `color{Brown}"Homo habilis"`

● Some of the bones among the bones discovered were `color{violet}"different"`.

● This creature was called the `color{violet}"first human-like"` being the hominid and was called `color{violet}"Homo habilis"`.

● The brain capacities were between `color{violet}"650-800cc"`.

● They probably `color{violet}"did not eat meat"`.

`star` `color{Brown}"Homo Erectus"`

● Fossils discovered in `color{violet}"Java"` in `color{Brown}"1891"` revealed the `color{violet}"next stage"`, i.e., Homo erectus about `color{Brown}"1.5 mya"`.

● Homo erectus had a `color{violet}"large brain"` around `color{violet}"900cc"`.

● Homo erectus probably ate `color{violet}"meat"`.

`star` `color{Brown}"Neanderthal Man"`

● The Neanderthal man with a `color{violet}"brain size of 1400cc"` lived in near `color{violet}"east and central Asia"` between `color{Brown}"1,00,000-40,000"` years back.

● They used `color{violet}"hides"` to protect their body and `color{violet}"buried their dead"`.

`star` `color{Brown}"Homo Sapiens"`

● Homo sapiens `color{violet}"arose in Africa"` and moved across `color{violet}"continents"` and developed into `color{violet}"distinct races"`.

● During `color{violet}"ice age"` between `color{Brown}"75,000-10,000"` years ago modern Homo sapiens arose.

● `color{violet}"Pre-historic cave"` art developed about `color{Brown}"18,000 years"` ago.

● `color{violet}"Agriculture"` came around `color{brown}"10,000 years back"` and human settlements started.

● The rest of what happened is part of human history of `color{violet}"growth and decline of civilisations"`.