Operationalizing evolutionary transitions in individuality

Area of Science:

• Evolutionary biology
• Developmental biology

Background:

• Evolutionary transitions in individuality (ETIs) are central to understanding life's complexity.
• Previous research lacked systematic operationalization of ETIs.

Purpose of the Study:

• To systematically operationalize the concept of ETIs.
• To quantitatively compare ETIs across taxa and levels of complexity.

Main Methods:

• Devised four indicators: system size, inseparability, reproductive specialization, and non-reproductive specialization.
• Conducted quantitative comparisons across multiple taxa and ETIs.

Main Results:

• Inseparability plays a crucial role in ETIs, appearing irreversible.
• Inseparability may signify the emergence of a higher-level individual.
• Disparate groups show similar progression patterns during ETIs.

Conclusions:

• The four indicators provide a framework for studying ETIs.
• Inseparability is a critical factor in the evolution of individuality.
• A universal pattern of progression exists for ETIs across different organisms.