Speciation, diversity, and Mode 1 technologies: the impact of variability selection

Area of Science:

• Evolutionary Biology
• Paleoclimatology
• Paleoanthropology

Background:

• Organisms face changing selective pressures due to environmental shifts over geological time.
• The variability selection hypothesis posits that increased environmental fluctuation promotes the evolution of complex, flexible behaviors for adapting to novel conditions.

Purpose of the Study:

• To test the variability selection hypothesis using a genetic model.
• To investigate the role of environmental variability in the evolution of complex behaviors and hominin adaptations.

Main Methods:

• A single-locus genetic model was employed, simulating competition between a 'versatilist' allele and two specialist alleles.
• The model used a fluctuating environment, initially a sine wave, then an empirical climate curve spanning the last 5 million years.

Main Results:

• Generalist alleles fixed in the sine wave environment, while versatilist alleles fixed in the empirical climate curve environment.
• Variability selection was a significant evolutionary force between 2.5 and 1.2 million years ago.
• Versatilist alleles showed fixation even with minimal fitness advantages over generalists in variable conditions.

Conclusions:

• Environmental variability, particularly between 2.5 and 1.2 Ma, likely favored flexible behavioral strategies.
• This climatic variability may have spurred the development of early stone tool technologies (Oldowan lithics).
• Heightened environmental variability could have driven hominin adaptive radiation and speciation/extinction patterns.