• Skip to primary navigation
  • Skip to main content
  • Skip to footer
  • About
  • Image & Use Policy
  • Translations
  • Glossary

SUPPORT UE

  • Email
  • Facebook
  • Twitter

UC MUSEUM OF PALEONTOLOGY

UC Berkeley logoUC Berkeley

Understanding Evolution

Understanding Evolution

Your one-stop source for information on evolution

Understanding Evolution

  • Home
  • Evolution 101
    • An introduction to evolution: what is evolution and how does it work?
      • 1_historyoflife_menu_iconThe history of life: looking at the patterns – Change over time and shared ancestors
      • 2_mechanisms_menu_iconMechanisms: the processes of evolution – Selection, mutation, migration, and more
      • 3_microevo_menu_iconMicroevolution – Evolution within a population
      • 4_speciation_menu_iconSpeciation – How new species arise
      • 5_macroevo_menu_iconMacroevolution – Evolution above the species level
      • 6_bigissues_menu_iconThe big issues – Pacing, diversity, complexity, and trends
  • Teach Evolution
    • Lessons and teaching tools
      • Teaching Resources
      • Image Library
      • Using research profiles with students
      • Active-learning slides for instruction
      • Using Evo in the News with students
      • Guide to Evo 101 and Digging Data
    • Conceptual framework
      • Alignment with the Next Generation Science Standards
      • teach-evo-menu-icon
    • Teaching guides
      • K-2 teaching guide
      • 3-5 teaching guide
      • 6-8 teaching guide
      • 9-12 teaching guide
      • Undergraduate teaching guide

    • Misconceptions about evolution

    • Dealing with objections to evolution
      • Information on controversies in the public arena relating to evolution
  • Learn Evolution

Home → Neutral theory: the relative importance of drift and selection
  • ES en Español

Neutral theory: the relative importance of drift and selection

It might seem like everywhere we look, we see evidence of natural selection: organisms seem to be pretty well adapted to their environments. But the neutral theory of molecular evolution suggests that most of the genetic variation in populations is the result of mutation and genetic drift and not selection.

Balance scale depicting the word "selection" on the plate on the left and "drift" on plate on the right. They are even with on another.
Download this graphic from the Image library.

Basically, the theory suggests that if a population carries several different versions of a gene, odds are that each of those versions is equally good at performing its job — in other words, that variation is neutral: whether you carry gene version A or gene version B does not affect your fitness.

The neutral theory is easily misinterpreted. It does NOT suggest:

  • That organisms are not adapted to their environments
  • That all morphological variation is neutral
  • That ALL genetic variation is neutral
  • That natural selection is unimportant in shaping genomes

The main point of the neutral theory is simply that when we see several versions of a gene in a population, it is likely that their frequencies are simply drifting around. The data supporting and refuting the neutral theory are complicated. Figuring out how widely the neutral theory applies is still the topic of much research.

Footer

Connect

  • Email
  • Facebook
  • Twitter

Subscribe to our newsletter

Teach

  • Teaching resource database
  • Correcting misconceptions
  • Conceptual framework and NGSS alignment
  • Image and use policy

Learn

  • Evo 101
  • Evo in the News
  • The Tree Room
  • Browse learning resources
  • Glossary

Copyright © 2023 · UC Museum of Paleontology Understanding Evolution · Privacy Policy