Question

3)Which of the following two hypotheses: 1) Progressive evolution of a single lineage and 2) Evolutionary radiation is supported by evidence? Describe the evidence while proving a brief explanation. (This topic is with regards to human evolution).

Answer 1

When a number of species originated or evolves from a single ancestral species, this type of evolution is called as adaptive radiation or radiation. It is generally takes place due to change in the environment which may provides a new resource or a new challenge to the organisms forcing them to change and hence many species formed from a single ancestral species. Evidences have shown that the modern day man called Homo sapiens are distinct species of the the hominid family, the great apes. Also their development has been found as per a web pattern and not as linear along with interbreeding with the other Hominis, hence all the evidences are denying the hypothesis that the human evolution is lineage and supports the 2nd hypothesis given in the question.

Hominoidea Hominidae Hylobatidae Homininae Ponginae Hominini Gorillini Homo Pan Gorilla Pongo Hylobates Superfamily Family Subfamily Tribe Genus

Evidence :

1. Molecular evidence (genetics):

The relative species of humans are found to be bonobos and chimpanzees (both genus Pan) and gorillas (genus Gorilla) and the molecular studies of their DNA have shown that they have 95 to 99% similarity between their DNA sequences. So from this we can deny the hypothesis of progressive evolution of a single lineage and by using molecular clock technique we can also calculate the time required for number of divergent mutations to accumulate between two lineages to make these lineages separate from each other.

Also it is found that, the gibbons (family Hylobatidae) and the orangutans (genus Pongo) are the first line of species deviated from the evolutionary lineage to give rise the species Homo sapiens.

2.Fossil record:

The fossil records found from different excavation sites also have confirmed that divergence of the gorilla, chimpanzee and hominin lineages takes place from the evolutionary lineage of the Hominoidea. The skull size was the focused part of the fossils to follow the evolutionary pattern.

As per the evidences collected from the above discussed technique, it is confirmed that the evolution of the humans don’t belonging to the progressive lineage of the Hominoidea, but it belongs to a number of lineages which at last gives rise to the modern humans. Hence the Homo sapiens have also found similarities with the other species belonging to other family and different genus.

if the above described evidence are not as per your answer, please specify which kind f answer you want.