The Genetic Book of the Dead — III. When a Difference Entered the Lineage

A difference appears in an organism.

Most differences disappear with it.

A variation may affect an individual without ever becoming part of the future of its lineage. For evolutionary history to accumulate, something else is required.

The difference must be inherited.

This makes biological history peculiar.

An organism can acquire a scar during its lifetime, and the scar can change how that organism lives. But the scar normally does not become part of the organisation of its descendants.

A genetic difference can.

If it is passed on, the difference enters another timescale.

It can encounter selection again.

And again.

And again.

Now the consequences of a past difference can become part of the conditions under which future organisms develop.

The lineage has acquired a new possibility.

This is why evolution is not simply a record of individual adaptations. It is a process in which some differences become available to future generations while others disappear.

Inheritance turns difference into history.

Selection then acts upon that inherited variation, altering its distribution across generations.

The process can be represented simply:

variation → inheritance → differential persistence → altered lineage.

The important point is that the lineage does not need to remember the event that produced the variation.

It only needs to carry forward the difference.

Over time, many such differences accumulate.

The organisation of the present organism therefore reflects not one past event but a vast succession of events whose consequences survived long enough to become part of the lineage.

This gives evolutionary memory its extraordinary depth.

An organism can carry consequences of environments that disappeared millions of years ago.

But there is also a limitation.

The inherited organisation is not a faithful record of the past.

It is what remained after the past had acted upon variation.

The genome therefore tells us about history indirectly.

It preserves the consequences of differential persistence, not the experiences of ancestors themselves.

And this returns us to our larger question.

History becomes organisation when a difference produced by the past survives into a system's future and changes what that future can do.

In evolution, inheritance is the mechanism that allows the difference to cross the boundary between generations.

The dead do not speak.

But their differential persistence has altered the organisation of the living.

And the living carry that altered organisation forward.