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Catlike sabre-toothed predators evolved in three distinct lineages of mammals – carnivorans like the sabre-toothed cats, and nimravids ("false" sabre-tooths), the sparassodont family Thylacosmilidae ("marsupial" sabre-tooths), the gorgonopsids and the creodonts also developed long canine teeth, but with no other particular physical similarities.
The fact that small cats have an ERV where the larger cats do not suggests that the gene was inserted into the ancestor of the small cats after the larger cats had diverged. [35] Another example of this is with humans and chimps. Humans contain numerous ERVs that comprise a considerable percentage of the genome.
Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonly referred to as the last universal common ancestor (LUCA) of all life on Earth.
Likewise, Y chromosome is present as a single sex chromosome in the male individual and is passed on to male descendants without recombination. It can be used to trace patrilineal inheritance and to find the Y-chromosomal Adam , the most recent common ancestor of all humans via the Y-DNA pathway.
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).
The term monophyly, or monophyletic, derives from the two Ancient Greek words μόνος (mónos), meaning "alone, only, unique", and φῦλον (phûlon), meaning "genus, species", [4] [5] and refers to the fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor.
A clade, a monophyletic taxon, is a taxon that consists of the last common ancestor and all its descendants. [31] A clade is characterized by one or more apomorphies: derived character states present in the first member of the taxon, inherited by its descendants (unless secondarily lost), and not inherited by any other taxa. Paraphyly
[9] Following Darwin's publication, Thomas Henry Huxley used the fossils of Archaeopteryx and Hesperornis to argue that the birds are descendants of the dinosaurs. [10] Thus, a group of extant animals could be tied to a fossil group. The resulting description, that of dinosaurs "giving rise to" or being "the ancestors of" birds, exhibits the ...