What is Adaptive Radiation?
It is the process by which many species originate from one species in an area and radiate to different areas. This phenomenon was first observed by Darwin when he traveled to a place called Galapagos Island. There he observed that there were finches with different types of beaks. So, he concluded that all of these finches radiated on the same island from a single ancestor finch. All of these finches developed beaks according to the kind of food available to them. Hence, they evolved from the conventional seed-eating finches to vegetarian and insectivorous. These finches later came to be known as Darwin’s finches.
Examples of Adaptive Radiation
The example of the adaptive radiation is the development of different Australian Marsupials from one single ancestral stock in the Australian subcontinent. This explains divergent evolution for the ancestral stock from which a number of species arise. But, if in a given geographical area, several adaptive radiations take place for various species, it gives rise to convergent evolution.
The human evolution was started since the first species of humans came into being i.e., 15 million years ago. Evolution of man can be categorized into each species as each milestone:
- Dryopithecus and Ramapithecus were the earliest men. They marked the first line of difference between man and ape. The Dryopithecus were closer to apes compared to Ramapithecus which were closer to human. However, both of them had a lot of hair all over their body and walked like gorillas.
- Some fossils have been obtained from some man like species near the area of Tanzania and Ethiopia some 3-4 million years ago. The fossils suggest their height to be less than 4 feet.
- Australopithecines existed around 2 million years ago and lived in African grasslands. They were basically fruit eater but pieces of evidence exist which show that they used weapons for hunting.
- Then came Homo habilis which was the first man like a stage in the evolution of man. They had brains 650-800 cc in size and were mostly vegetarians.
- Homo erectus existed about 1.5 million years ago. The brain size increased to 900cc and they probably were the meat eater.
- The Neanderthal man existed in and around the east and central Asia about 100000-400000 years ago. They had the brain with the highest volume i.e., 1400cc. They showed modern day humans like practices of covering their body and burying the dead ones.
- Homo sapiens or the modern man arose during ice age about 75,000 – 10,000 years ago. They gradually developed into what we are today over the period of time with similar life processes.
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