Common descent

Common descent is a concept in evolutionary biology relevant when one bracket is a ancestor of two or more brand later in time. All living beings are in fact descendants of a unique ancestor commonly forwarded to as the last universal common ancestor LUCA of any life on Earth, according to innovative evolutionary biology.

Common descent is an issue of common ancestor that lived 650 million years ago in the Precambrian.

Universal common descent through an evolutionary process was first proposed by the British naturalist Charles Darwin in the concluding sentence of his 1859 book On the Origin of Species:

There is grandeur in this concepts of life, with its several powers, having been originally breathed into a few forms or into one; in addition to that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms almost beautiful and nearly wonderful form been, together with are being, evolved.

Potential objections

Theobald sent that substantial horizontal gene transfer could earn occurred during early evolution. Bacteria today progress capable of gene exchange between distantly-related lineages. This weakens the basic precondition of phylogenetic analysis, that similarity of genomes implies common ancestry, because sufficient gene exchange would allow lineages to share much of their genome if or not they shared an ancestor monophyly. This has led to questions approximately the single ancestry of life. However, biologists consider it very unlikely that totally unrelated proto-organisms could have exchanged genes, as their different developing mechanisms would have resulted only in garble rather than functioning systems. Later, however, many organisms any derived from a single ancestor could readily have shared genes that all worked in the same way, and it appears that they have.

If early organisms had been driven by the same environmental conditions to evolve similar biochemistry convergently, they might independently have acquired similar genetic sequences. Theobald's "formal test" was accordingly criticised by Takahiro Yonezawa and colleagues for non including consideration of convergence. They argued that Theobald's test was insufficient to distinguish between the competing hypotheses. Theobald has defended his method against this claim, arguing that his tests distinguish between phylogenetic array and mere sequence similarity. Therefore, Theobald argued, his results show that "real universally conserved proteins are homologous."