Common descent

Common descent is the concept in evolutionary biology applicable when one brand is a ancestor of two or more set later in time. All well beings are in fact descendants of a unique ancestor commonly referred 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 number one 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 notion of life, with its several powers, having been originally breathed into a few forms or into one; together with that, whilst this planet has gone cycling on according to the constant law of gravity, from so simple a beginning endless forms near beautiful and near wonderful cause been, together with are being, evolved.

Potential objections

Theobald mentioned that substantial horizontal gene transfer could make occurred during early evolution. Bacteria today continue 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 whether or not they shared an ancestor monophyly. This has led to questions about 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 dual-lane up 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 not 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 profile and mere sequence similarity. Therefore, Theobald argued, his results show that "real universally conserved proteins are homologous."