Evolution of Life (Biology)

While natural selection is a central mechanism, other evolutionary processes like mutation, genetic drift, and gene flow also play a role in shaping populations and the evolutionary process.

1. Use and disuse of organs – Individuals lose characteristics which they do not require (or use) and develop characteristics that are useful.
2. Inheritance of acquired traits – Individuals inherit the acquired traits of their ancestors.
   In the context of organic evolution as explained by Lamarck, the loss of limbs in snakes is explained by the phenomenon of the use and disuse of organs.

Amongst the basic factors, gene and chromosomal mutations have been recognized as the ultimate sources of biological changes and hence, the ultimate 'raw material' of evolution.

Gene recombination, the third basic factor, then increases the variability of individual genotypes in a population.

Mutations result from damage to DNA which is not repaired or to RNA genomes (typically caused by radiation or chemical mutagens), errors in the process of replication or from the insertion or deletion of segments of DNA by mobile genetic elements.

Mutations play a part in both normal and abnormal biological processes including evolution, cancer, and the development of the immune system. Among living organisms, it is the most responsible factor for bringing about the origin of a new species.

Cro-Magnon is a common name that has been used to describe the first early modern humans. The earliest known remains of Cro-Magnon-like humans are radiocarbon dated to 43,000 years before. Cro-Magnons were robustly built and powerful.

Their body was generally heavy and solid with a strong musculature. The face was short and wide. The chin was prominent. The brain capacity was about 1,600 cubic centimeters, larger than the average for modern humans.

However, recent research suggests that the physical dimensions of so-called "Cro-Magnon" are not sufficiently different from modern humans to warrant a separate designation.

The Denisovans or Denisova hominins are an extinct species or subspecies of archaic human that ranged across Asia during the Lower and Middle Paleolithic.

The first identification of a Denisovan individual occurred in 2010, based on mitochondrial DNA (mtDNA) extracted from a juvenile female finger bone excavated from the Siberian Denisova's Cave in the Altai Mountains in 2008.

Nuclear DNA indicates close affinities with Neanderthals. Additional specimens from Denisovan's Cave were subsequently identified, as was a single specimen from the Baishiya Karst Cave on the Tibetan Plateau.

DNA evidence suggests they had dark skin, eyes, and hair, and had a Neanderthal-like build and facial features. However, they had larger molars which are reminiscent of Middle to Late Pleistocene archaic humans and australopithecines.

Extinct mammoth is more closely related to today's African elephant or Asian elephant. Modern elephants and woolly mammoths share a common ancestor, that lived about 6 million years ago.

Genetic studies show that Asian elephants are more closely related to mammoths than African elephants. The split between the ancestor of mammoths and Asian elephants happened around 6 million years ago.

African elephants diverged from this lineage earlier. The woolly mammoth (Mammuthus primigenius) evolved from steppe mammoths (Mammuthus trogontherii) in Asia, spreading to Europe and North America over time.