Succinct Definition of Biological Evolution

  1. Anyone exposed to academic rigor would find the use of the term "biological evolution" to be rather vague.

    There is something about Darwin and common descent and then it starts to get somewhat vague.

    Is there a definitive definition of "biological evolution"?

    I offer this in the spirit of Niels Bohr - "Atomic Physics and Human Knowledge".
  2. jcsd
  3. Evolution is the change in allele frequencies (or you could just say change in general, because epigeneticss is also a part) in a population over time. There's no need to be any more specific for the same reason dictionary writers don't feel the need to define words within a word's definition. If you need more clarification, you can look deeper into it elsewhere.
  4. Moreover, the term biological evolution is typically used to distinguish it from the evolution of stars, or planetary systems, or the universe itself. In those contexts evolution means the changes that occur over time to the respective systems.

    I sense that the need for the phrase biological evolution has arisen, in part, to counter creationists who conflate these terms and use faulty logic based on that conflation in an attempt to discredit biological evolution. Adding the adjective helps to, rightly, separate them.

    aroc91 has given the current, generally accepted definition. Palaeontologists would tend to use a somewhat different one, since they can view only phenotypes, not genotypes.

    However, I would suggest that a precise definition is unnecessary. We do not have a precise definition of life, yet we are able to recognise it in many forms and study it in immense detail. So to with evolution.
  5. "Descent with modification." How's that for succinct?:cool:
  6. Very good. It incorporates the concept of allele frequency and phenotype changes, thus satisfying biologists and palaeontologists respectively, while demonstrating that old Charlie had a knack for a nice phrase.
  7. Gotta love good ole' Charlie.
  8. Ryan_m_b

    Staff: Mentor

    Descent with modification under environmental attrition is one I've heard several times before. It's a good, brief and encompassing definition. Offspring are slightly different to parents, the environment means that some of them get to reproduce more. That's the fundamental of it.
  9. Ygggdrasil

    Ygggdrasil 1,748
    Science Advisor

    This is a good definition for natural selection, but natural selection is just one mechanism by which evolution can occur. Genetic drift, founder effects, and bottlenecks can all cause evolution but are not driven by environmental attrition. Personally, I would favor the definition as changes in allele frequencies over time. It gives no information about how or why evolution occurs, but it is a perfectly fine description of what occurs in evolution (though one could argue that it captures mostly microevolution and not macroevolution).
  10. I like that one too, got a nice ring to it, succinct, pithy, and concise..And it even rhymes!:thumbs:
  11. Ryan_m_b

    Staff: Mentor

    Of course, but if we're being succinct then we're not going to cover everything. A succinct definition is only really going to be needed with people unfamiliar with the subject matter, in which case natural selection is the best place to start and build upon that.
  12. The phrase "allele frequencies" is often repeated in the above. What is an "allele"? To me it is a difference in the sequence of amino acids that code for a protein. However, the sensitivity of the amino acid chain if vague. How many errors are required for an "allele".
  13. How so? Any sequence change creates a new allele. All it takes is one.
  14. Ygggdrasil

    Ygggdrasil 1,748
    Science Advisor

    An allele is any genetic variant (i.e. change in a DNA sequence). These changes do not have to be in coding regions. For example, the allele for lactase persistence (not having lacose intolerance) is a mutation in the non-coding sequence upstream of the coding sequence for the lactase enzyme. These changes in the promoter region of the lactase gene prevent it from being turned off in adulthood, allowing individuals with this allele to be able to digest dairy products as adults.

    It is often difficult to predict whether certain changes in the amino acid sequence of a protein will have an effect. Sometimes a single amino acid change will cause a drastic change in the function of the protein (e.g. in many genetic disorders such as hemophilia), but often, many amino acids in a protein can be mutated without much effect. While scientists can often make decent guesses as to whether a mutation to a coding sequence will likely alter the function of the encoded protein (for example, by looking to see how often that particular amino acid in the protein has been mutated throughout evolution), we still have problems predicting the effects of mutations, especially in non-coding DNA sequences.
  15. Biological evolution is many things.

    It is a science, it is a process, it is a fact of its observation, it is a theory predicting the process details and, more than in many sciences, it is a history (set of pathways) actually taken, it is the constraint that we look at organisms*.

    Here I would go with a process definition.

    A succinct process definition I have seen is "differential reproduction", which encapsulates "descent with modification" with all its mechanisms and frames the population genetic definition.

    If the question is to make the correspondence to other processes clearer I would perhaps say "evolution is the process that changes the genome of a population [over generations]". Compare with "gravitation is the process that changes the acceleration of a test mass".

    The question is what the definition is to be used for? Definitions are often more or less superfluous outside of mathematics and dictionary usage. Say, "academic rigor" := science rigor mortis. :)

    *Which is yet another definitional question. Turtles upon turtles, and all that.
    Last edited: Oct 17, 2014
  16. In the spirit of the anthropic principle, "I'm still here - sequence me"
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