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We developed complex structures like eyes and brain, whose mechanisms rely on specific species of molecules and relevant chemical reactions. But we did not develop an enhanced night vision, the ability to fly, or a built-in silicon-based integrated circuit.

As I understand, we did not develop the latter set of abilities because they are either not so much needed, cost too much energy to be beneficial, or that they required so many information to be coded into our genome that it would take forever for the mankind to produce sufficient mutations. But could this be quantified? Can we tell if a species will develop a specific character, based on the environment they're in?

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  • $\begingroup$ By "we", do you mean humans or animals in general? $\endgroup$ – kmm Sep 30 '15 at 12:16
  • $\begingroup$ I don't think so. You can say, if I throw this fresh water fish into salt water it will have to evolve or die. You could even say that a population living in a delta where they are exposed to fresh or salt water could possibly develop mechanisms for both. But you couldn't say with any certainty that they will. Maybe the species moves further inland as they get better characteristics for fresh water. I doubt that antibiotic resistance was predicted to occur before we started seeing it in labs. $\endgroup$ – Nathan Sep 30 '15 at 14:51
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    $\begingroup$ "But could this be quantified" -- what is "this" in this sentence? What is it that you wonder whether it is quantified or quantifiable? You have to be looking for numbers somewhere, so could you state which numbers you are after? Your last sentence seems less directly related to quantification. $\endgroup$ – Chelonian Sep 30 '15 at 15:47
  • $\begingroup$ There are some suggestions that evolution is quite predictable, more predictable than many of us think. Richard Dawkins is one proponent. If this is true, there is indeed some elements of predictability in the higher-level results of evolution. $\endgroup$ – Alex Sep 30 '15 at 16:01
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Can we tell if a species will develop a specific character, based on the environment they're in?

This is a major part of what quantitative genetics does. Or more detailedly, quantitative genetics can predict, for a population, changes in a trait given a selection pressure. First of all, for evolution to occur there must be variation in the trait you are making predictions about. Secondly the accuracy of the scale of the predictions matter greatly for the evolutionary model to be tested (eg, "Will body size increase?" vs "Will incisors increase 3mm in 300 generations?").

Several things have to be known to predict the evolution of a given trait:

  • The number of genetic sites controlling this trait (QTL, or quantitative trait loci). If the all the loci for a trait are known, the nucleotide heterogeneity within the population of those sites can be quantified. The number of genetic loci are important for estimating how often they will change from new mutations.

  • The effect of each genetic locus on contributing to variation to the trait (additive genetic effects).

  • The heritability of the genetics controlling this trait, (does the environment contribute to variation in the trait (low heritability) or do genetic differences cause more variation in the trait).

  • The strength and consistency of selection (how fit are individuals in that environment along to phenotypic distribution compared to previous generations). Is this trait being selected in isolation, or are other traits which share the same QTL also under selection.

  • The effective population size.
  • The rate of migration between this and other populations.

So yes, given the our knowledge of quantitative and population genetic theory, predicting evolution of a given trait is possible. Just as predicting the future is possible with the laws of physics if you know the position of every atom in the universe. It's important to remember that organisms are constellations of 'traits', so predicting the evolution of all traits which make up the individuals within a species could be similar to predicting the futures of several multiverses.

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Clarification on the question

The question is a little unclear and I will try to interpret it and answer it. I hope I won't fail to see your goal.

Quantitative vs predictive

There is a big difference between quantitative and predictive. To understand the difference you might want to ask the question on Philosophy.SE.

Quantified vs quantifiable

As @chelonian said in the comments, if you are asking Is evolution quantitative, then you would need to say whether you meant quantified or quantifiable. Almost everything in evolutionary biology (just like in other sciences) is quantifiable but most of it is not quantified as it takes a lot of money and time to do so.

What I think you are trying to ask

Paying attention to the question in your post Can we tell if a species will develop a specific character [..] and assuming that by develop, you meant evolve, then what you meant is Is evolution predictive rather than quantitative.

What I am answering

I will try to answer to the question How good are we to predict future evolution? and just say a few words about how quantitative a science is evolutionary biology.

Evolutionary Biology is a quantitative science

Evolutionary Biology is definitely a quantitative science. It relies a lot on mathematical modelling (incl. statistics and probability theory) and numerical modelling. You might for example want to have a look at Population Genetics and Quantitative Genetics which are at the core of evolutionary Biology.

What are we good at predicting?

Here are a few examples of things we can predict. We can predict how many pairwise differences (or other measures of molecular differentiation) do we expect between two lineages that recently split in a given number of years. We can predict how many mutations of a given fitness effects (whether beneficial or deleterious) do we expect to accumulate over a given period of time in a population. We can make also some predictions about the evolution of multicellularity, sociality, etc. in lineages that are limit-cases (relating again to our ability at a short time only). We can make predictions about the speed of evolution measured in Haldanes or in Darwins (these are units) if we know the genes involved and the heritability of the trait of interest. We can predict the heterozygosity of a structured population. I could cite many other examples. Generally speaking, we have good predictive abilities at short time scale OR for neutral sequences OR for conserved (DNA) regions (strong purifying selection).

In short, we can predict a lot of things but by far not everything yet.

What are we bad at predicting?

I would suggest to decompose the reasons for why predictions can be hard into the following categories. However, I might well forget something and one could argue that my semantic is less helpful some other semantic.

  • Environment
    • One issue related to make predictions at long time scale is that the environment changes through time in a way that we are not able to predict accurately enough yet.
  • Noise
    • I am not here talking about measurement error or sampling error (these are concept of statistics you may want to check if you don't know them), I am talking about the stochastic process that are inherent to biological systems such as the randomness of mutation processes and genetic drift.
  • Genotype-phenotype map
    • We have too little understanding of molecular genetics in order to be able to predict how different specific mutation would affect the phenotype. As a consequence, we today still have very little predictive power about the evolution of a phenotypic trait that is currently totally inexistent.
  • Complex systems
    • For example: demography affects evolution which affects the social environments, which affects demography which affects pattern of species competitions which affects the evolution of another species which affects its demography which affects the evolution of a third species which affects the demography of our first species, etc... These kind of complex systems are often mathematically not tractable.
  • Parameters
    • We often don't know the exact parameters of the lineage we are interested in. There is a lot of measures to take to be able to make predictions and we often don't have the money (or the time) to make all these measurements (assuming we are able to accurately measure them). For this reason, we are often relatively good to make predictions for a few model organisms but pretty bad for the vast majority of species.

I apologize for my total lack of reference but it would take hours to search references for every claim

Applications of evolutionary biology

There are not a lot of applications of evolutionary biology for the moment but still there are some proving its predictive power. These applications include

  • medicine and epidemiology (incl. evolution of resistance)
  • artificial selection and other technics mainly to improve crops nut not only
  • Various search algorithm such as genetic algorithm

General Advice

The best way to learn about evolution and to answer your own questions (or help you to ask more accurate questions) is to actually take a short course. Understanding Evolution by UC Berkeley is probably a good place to start.

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