Lineage (genetic)

A genetic lineage is a series of mutations which connect an ancestral genetic type (allele, haplotype, or haplogroup) to derivative type. In cases where the genetic tree is very bushy the order of mutations in the lineage is mostly known, examples are the order of mutations between E1b1b and E1b1b1a1a for the human Y-chromosome. In other instances the order of mutations may not be known, an example is the sequence of mutations between the L0/L1 split for human mitochondrial DNA and the basal L0 or L1 nodes.

A genetic lineage can be contrasted with an evolutionary lineage in that a genetic lineage applies to a locus. An example of the difference is that ancient African ape evolved into proto-gorilla and a chimpanzee-human ancestor, which further evolved into chimps and humans. While most human lineages coalesce with chimpanzee lineages, which then converge with gorilla lineages, a few human lineages coalesce with gorilla lineages and then converge with chimpanzee lineages (or chimpanzee lineages that coalesce with gorilla lineages and then converge with human lineages). This occurs because the speciation that marks evolutionary lineages occur as non-discrete events that are composed of 10s to 10000s of individuals in each developing taxa. This allows many variant lineages to be passed millions of years (See 2N-rule; 2 * 20 year/generations * 10,000 inds * ploidy) allows multiple deeply rooted lineages to be passed millions of years, over 2 or more speciation events. Such lineages may randomly undergo fixation at any time.

Basal lineage
In genetics a basal lineage is a genetic lineage that connects a variant allele (type) possessed by a more common ancestor that evolves into two descendant variants possessed by a branch ancestor. An example of a basal lineage is the lineage between mitochondrial 'Eve' and L0 or L1. Basal lineages may have types that are no longer represented in the extant population, only being defined by derivative types such as CRS for L1.

Peripheral lineage
Peripheral lineage (Also: surface lineage) are lineages in which interconnect an extant type to a branch ancestor.