The traditional theory states that complex life arose from competition and cooperation among organisms.

However, there are two important problems with this traditional theory:

1- The fossil evidence shows that complex life did not form in this way. Organisms suddenly appear in the fossil record - already complex.

2- Darwinian competition between species could not have been the only driver of the evolution of complexity, since it was competition within species - as well as the cooperation of their cells - that facilitated complexity evolution.

An inside-out theory of complexity evolution overcomes these problems.

The idea of an "inside-out" evolution of biological complexity, suggests that genomes themselves can undergo complexity evolution.

It involves competition and cooperation between selfish genetic elements within the genome rather than between species.

For example, transposons are repetitive DNA sequences that can move around within a genome. Transposons can provide beneficial and harmful effects to the genome, contributing to evolution.

Additionally, genomes are complex systems that self-organize and create new genetic and epigenetic changes. These changes give rise to new phenotypes, which can undergo natural selection at the organism level. This inside-out mechanism offers a more comprehensive explanation for the evolutionary origins of complex biological systems.