Quotes About Germ-line

A replicator may be said to 'benefit' from anything that increases the number of its descendant ('germ-line') copies.

Replicators may be classified in two ways. They may be 'active' or 'passive', and, cutting across this classification, they may be 'germ-line' or 'dead-end' replicators.

A germ-line replicator (which may be active or passive) is a replicator that is potentially the ancestor of an indefinitely long line of descendant replicators. A gene in a gamete is a germ-line replicator. So is a gene in one of the germ-line cells of a body, a direct mitotic ancestor of a gamete.

A DNA molecule in the germ-line of an individual who happens to die young, or who otherwise fails to reproduce, should not be called a dead-end replicator. Such germ-lines are, as it turns out, terminal. They fail in what may metaphorically be called their aspiration to immortality. Differential failure of this kind is what we mean by natural selection.

But whether it succeeds in practice or not, any germ-line replicator is potentially immortal. It 'aspires' to immortality but in practice is in danger of failing.

As I said, the active/passive distinction cuts across the germ-line/dead-end distinction. All four combinations are conceivable.

If replicators exist that are active, variants of them with certain phenotypic effects tend to out-replicate those with other phenotypic effects. If they are also germ-line replicators, these changes in relative frequency can have long-term, evolutionary impact.

To the extent that active germ-line replicators benefit from the survival of the bodies in which they sit, we may expect to see adaptations that can be interpreted as for bodily survival.

To the extent that active germ-line replicators benefit from the survival of bodies other than those in which they sit, we may expect to see 'altruism', parental care, etc.

To the extent that active germ-line replicators benefit from the survival of the group of individuals in which they sit, over and above the two effects just mentioned, we may expect to see adaptations for the preservation of the group.

Germ-line replicators, then, are units that actually survive or fail to survive, the difference constituting natural selection.

CRISPR-enabled 'gene drives' enable us to make changes to the germ-line of organisms permanent such that changes spread through the entire wild population, including making species extinct on demand. Unlike nuclear weapons such technologies are not complex, expensive, and able to be kept secret for a long time.