There are no “laws” in evolutionary biology comparable to those in physics, except perhaps that “all species evolve”. But that’s not very exciting. What we have in my field are not unbreakable “laws,” but patterns or generalizations. When these become sufficiently general and impressive (i.e. 80-90% of species obey them, often across diverse taxa), then we have an area of research where explanations can be general. A lot of good evolutionary biology consists of case studies that don’t elucidate a previously understood pattern, and lots of those studies good, or even iconic —Peter and Rosemary Grants’ paper on the evolutionary increase in beak size of Geospiza fortis due to a drought is one example. It serves as an iconic example of natural selection, but doesn’t shed light on how natural selection works in other cases—and it’s no worse for that.
In my own work I’ve often tried to elucidate the genetic/evolutionary basis of these broad patterns, hoping that a simple and general explanation could at one stroke explain many “anecdotes.” I’ll simply describe below what I see as “laws of evolutionary biology”: those generalizations which hold sufficiently strongly that explaining them in one group might also give explanations for all groups. And I think we now know at least the partial biological basis for each of these “laws”?
- If only one of the two sexes of a species is brightly colored, ornamented, or advertises itself to the other, that sex is usually the male. The explanation, first given by Darwin but subject to much recent work, is sexual selection, and we have a good understanding of how it works, but not necessarily why females in a population prefer one type of male over another. The evolutionary basis and mechanics of female preference is an active area of research.
- If there is only one trait that can be used to distinguish members of different species, that trait is very often the shape or behavior of the male genitalia. This is the subject of William Eberhard’s excellent but underappreciated book, Sexual Selection and Male Genitalia, a must-read for evolutionary biologists. (It’s out of print now, I think, but you can get it from your library.) The answer appears to be sexual selection on those genitalia, implying that females can detect the differences in shapes as they evolve within a species—leading to differences between species. The fact that such characters are often diagnostic means that sexual selection on male genitals must be a potent and ongoing evolutionary force within species. (It’s interesting that in those groups where sperm is not transferred via the genitalia but by organs like spider pedipalps, it is the sperm transferring organs that are diagnostic, supporting the sexual-selection explanation.)
- If in crosses between two closely-related species, only one sex among the hybrids is inviable or sterile, it is almost invariably the heterogametic sex (the one that has two unlike sex chromosomes). I spent much of my career working on this phenomenon, which holds widely: in insects, mammals, birds, worms, and so on. The generalization is called “Haldane’s rule” after its publication by the evolutionary geneticist J.B.S. Haldane in 1922. In the last 90 years the rule has been strengthened, holding widely across animals. And it holds regardless of which sex is heterogametic. In mammals and many insects, for instance, in which males are XY and females XX, the males are sterile or inviable in species crosses. But in birds and butterflies, in which females are heterogametic and males homogametic (having similar sex chromosomes), it is the females who are preferentially sterile or inviable in species crosses. This suggests that the cause of Haldane’s rule isn’t connected so much with one gender evolving faster than the other, but with the sex chromosomes themselves.
- In crosses between species, the genetic cause of the preferential sterility/inviability of the heterogametic sex resides on the sex chromosomes. I worked a lot on this problem too, and it’s deeply connected with “law” #3. If genes for inviability or sterility act as recessives in hybrids, for instance, then every such gene in a hybrid’s heterogametic X chromosome will be expressed, and that individual will be sterile or inviable. (Males in XY species, for instance, will express every single gene on the X chromosome in hybrids: usually the Y has few genes. But females, being XX, will have every deleterious recessive masked by a dominant allele on the other sex chromosome, and so will be more fit.) This is called the “dominance theory,” and there’s a lot of evidence supporting it. Recessive genes that debilitate hybrids are also found on the autosomes, but are not expressed in first-generation species hybrids and so don’t cause Haldane’s rule. The other explanation for the “X-effect” is that the X chromosome evolves faster than the autosomes (non-sex chromosomes), and so deleterious interactions in hybrids will involve that chromosome more often. That, too, appears to play a role in Haldane’s rule, but probably not as large a role as the “dominance hypothesis.”
Readers are welcome to add to this list of evolutionary biology “laws,” for these are the only ones I can think of that hold so widely.
Reblogged this on perfectlyfadeddelusions.
Basically, evolutionary biology is one sexy puzzle after another.
Yessssss!!!
Funny, but the transphobia in this post is highly offensive. “THE two sexes…?” Like transpersons and non-binary people don’t even exist? The words “male” and “female,” of course, are very problematic. And the way you (Jerry) throw them around with no trigger warnings or disclaimers is appalling. Check your white, misogynist, hetero, cis privilege, okay?!? It’s unreal that in the year 2015 we still have to deal with “scientists” basically telling us that the laws of nature all revolve around the size and shape of penises. GENDER IS A SOCIAL CONSTRUCT!!! Here’s a Law of Biology for you, the preferred pronoun of all racist, Islamophobic, colonialist, fascist, neo-con, New Atheists (redundant, I know) is always “he.” Anyway, I’m calling the police. This is offensive and it should not be allowed!
(Sarcasm, of course. But I wouldn’t be surprised to see something like this crop up on some other blogs. I’d be almost a given, in fact, had the OP been tweeted by Dawkins.)
The comedy is, of course, that Jerry’s post is concerned with, essentially, chemistry (which of two sets of paired polymers contains more long similar sections, or in biological-speak, is homogametic), while pacopicopiedra’s parody is concerned with the social constructs of meatbags full of dirty water.
One of the laws is that mutants reproduce (Call this the Mutant Reproduction Law). Yet it is exceedingly unlikely that a mutant could find a mate, because oppressive standards of beauty are all-the-rage. Why then can evolution be true? It can’t be! Its laws hoist it by its own pitards!
NS
I stopped studying science at school at the age of fourteen, and even I can see that this displays both a lack of understanding of evolutionary theory and faulty logic.
Not sure if this is some sort of very subtle joke?
However, please note ‘petard’. Has an ‘e’ and is generally not in the plural.
Oh my no, he’s not joking. Went to his webpage and he’s being completely serious.
The first pattern that attests to the validity of the first of “Kohl’s Laws of Biology” is that all living genera must eat to reproduce. Thermodynamic cycles of protein biosynthesis and degradation link the epigenetic landscape to the physical landscape of DNA in all living genera.
No organism that has ever contributed to the earth’s biomass appears to have automagically evolved, which makes all the claims of evolutionary theorists appear to be absurd.However, keep in mind that the works of this year’s Nobel Laureates in Medicine will continue to force all theorists to reassert their ridiculous claims or abandon them before the evolution industry and big bang cosmology industries implode, and return to their origins in lawlessness with patterns.
Your comment is gibberish. For example: “All living genera”. Genera is a term applied in systematics that encompasses a group of closely related species. It denotes a common ancestor between the same species existed at some point in the past. Indeed, organisms consume other organisms of one kind or another, are symbiotic in some fashion to gain nutrients, or may entirely draw all nutrients from minerals. Thermodynamic cycles. What? What does epigenetic landscape mean? Epigenetics involves the expression of genes given some environmental signal. This signal need not be induced during the lifetime of the organism, but may be heritable from an ancestor. I can’t bear to comment on the rest. Perhaps another brave person can do better. These are demonstrable facts which you can discover by reading the scientific literature or a recent textbook. You are of course welcome to replicate the studies.
Perhaps the comment was over-the-top sarcasm. /shrug
Thanks.
Re: “Your comment is gibberish.”
I get that a lot. Only from biologically uninformed science idiots, but there are more of them than there are serious scientists who would first perform a google search on “RNA mediated” to see that evolutionary theorists have been touting only pseudoscientific nonsense for several decades.
That’s really something considering my background in evolutionary biology. At any rate, I did look at some of your papers. It is clear you have ideas on epigenetics, many which seem entirely plausible. Your discussion is all over the place and you draw conclusions which go far beyond the evidence you quote from. My comments on how you munge concepts astands.
“Hoist on his own petar'” was Hamlet’s little French fart joke on Claudius (via Rosencrantz and Guildenstern).
“notedscholar” strikes me as a parody hoaxster.
The expression is ‘hoist BY his own petar’, and means to be blown up by his own petard, which is a small bomb. In modern parlance, we could use by or with, but not ‘on’. Hamlet III.iv.207-208.
The petard was essentially the medieval analogue to C-4 plastique, used to breach castle doors and similar structures. The term is derived from the French word for “breaking wind,” owing to the similarity of sound between that phenomenon and the detonation of a small bomb.
Both the bomblet and the fart serve as apt metaphors for what happens when Rosencrantz and Guildenstern present Claudius’s letter (covertly altered by Hamlet) to the King of England. What a piece of work were those men!
Dear not-at-all-noted-not-a-scholar,
A typical human has about 50 novel genetic mutations in them. Every single human being is thus a “mutant”. It is simply not true that it is “exceedingly unlikely” that such “mutants” would find a mate — every single child you see around you is the child of two “mutants”.
You have one of the classic misunderstandings of evolution: You think that evolution is about a small number of mutations, each of which has a large effect. That’s wrong. Evolution is actually about a very large number of mutations, most of which have very little effect.
well put, Coel.
I’m pretty sure this is a joke. Notice the anti-Einstein gravatar? That’s a reference to Andy Schlafley’s Conservapedia. And also note that the argument is similar to Ray “bananaman” Comfort’s “First male can’t find the first female” argument.
But in an age of Poe’s law I suppose I cant be all that certain.
A mutation still spreads even if only one parent has it initially. It also doesn’t mean that it immediately must spread through the entire species. Natural selection acts slowly on variation within a population.
I think you’ve watched too many X-Men movies.
Blue eyes are a mutation.
Of course that is true of all genetic features.
Of course there’s a Mutant Reproduction Law–where else did Donald Trump come from?
The deranged coupling of several pathetic hairpieces?
Pathetic Hairpiece Orgy.
All together now: “sounds like a good name for a band.”
😀
“Pass the Sick Bucket” were a punk band in the 70s. For a couple of weeks.
The idea of actually passing a sick bucket makes the idea of passing a kidney stone sound positively desirable.
Now I know it’s possible to EEUW! & LOL simultaneously.
You’ll be glad to know that the manager stole all the money. Which wasn’t much.
I think there was an open $5 mil bet that Trump’s parentage involved at least one orangutan.
Ha Ha Ha!
Would it be reasonable to suggest that females already carry a significant burden in producing young that there’s more of a budget left over for the males to be extravagant with resources?
That is, there’s a cost for being showy: you’re easier for predators and prey to spot, you’ve got these huge appendages to build and haul around and maintain, and so on. If you’re already paying a significant price to produce eggs, tend to their birth, care for them afterwards, and so on…you’re less likely to be able to afford such extravagances in the first place. But if you’re built from the same basic plan as one that can afford to put lots of resources into reproduction but you don’t actually have the burden of reproducing, it’s to your advantage to put those surpluses to convincing those with the heavy burden to put their burden to your use.
A way to test this idea would be to examine the gender roles for species in which the females are the showy ones. If the males are the ones who put the most effort into providing for the next generation….
Cheers,
b&
Yes, seahorses and phalaropes work — you simply substitute “stuck with the kids” for “female”…
But it’s not as simple as males have more surplus, rather that microgametes are cheap and easily produced in any quantity. Macrogametes not so much.
Which is a distinction that works for single-celled sexual organisms too.
When the sexes contribute unequally to reproductive effort (investment of time and energy in the production and care of offspring), the sex that invests less (usually the male) tends to evolve ornaments. There seems to be a “growing” consensus that one important reason for this (in promiscuous species, in which males do not contribute to the care of their offspring) is that ornaments are good indicators physiological quality (i.e., good genes). Examples of promiscuous birds with highly ornamented males that engage in long, complicated mating displays include birds-of-paradise, manikins, bower birds and hummingbirds. Spiffy ornaments attest that a male is well fed (and despite the burden, he can find plenty of food), is not washed out or saggy from parasitism (i.e., has a good immunological system), and, despite the encumbrance of being conspicuous and weighted-down, retains an undeniable savy to evade predators. Presumably these physiological qualities will be inherited by daughters as well as sons: the daughters will tend to grow up to be successful moms and the sons much preferred mates. Females can trust the genetic quality of males that bear bright, shiny ornaments. This concept is called the “Handicap Principle” (see Wikipedia).
However, the handicap principle only works if the ornament is less costly to an individual in good condition (or whatever the measure of “quality” is) than to one in poor condition. And the benefit applies to sons as well as daughters. (If I recall, it was John Maynard Smith who showed both of these.)
I believe there’s something to what you say, but I’d say it rather differently. When one sex provides a costly resource, there’s competition for mates and thus sexual selection on the other sex (which may involve bright colors). Most often, it’s only females who provide that resource. In a fairly small number of species, it’s only males (e.g. phalaropes and jacanas). In a reasonably large number of species, it’s both (e.g. birds in which both sexes are fancy). The main female resource is generally big, well-provisioned eggs. The main male resource is most often extensive parental and/or mate care.
I was going to suggest similarly that the law not be specific about which sex is which, since sometimes it is the female that is under selection to be ornamented, or to otherwise compete for males.
In the more general sense of the law, it can be said that if one sex has higher reproductive cost than the other sex, then that sex becomes choosy about their mates and becomes a limited resource for which the other sex must compete. The outcome of this competition often results in selection for the more available sex to become ornamented for the traits that improve its chances to be chosen.
I wonder if the degree to which (2) is true depends on the degree to which the female and male genitalia meet as a “lock and key” mechanism during copulation (as in most arthropods). I haven’t read Eberhard’s book, but does it hold as strongly for, say, mammals and birds?
The nice thing about (1) is that the exceptions (females are more brightly colored) usually prove the rule. Species in which the females are showier (e.g., phalaropes) are often polyandrous and there is high male investment in offspring.
There’s not much evidence for the lock and key hypothesis, as Eberhard notes. What is clear is that male genitalia seem to evolve within a species faster than virtually all other traits, and that demands explanation.
In spawning organisms too?
I believe most, if not all, broadcast spawners lack copulatory/ intromittent organs.
That occurred to me as soon as I hit “Post Comment…” 🙄
I’ve heard it claimed, but don’t know whether it’s true, that (for birds at least) if the two genders are similar in plumage, then they are monogamous and that both take care of the young. This fits with my experience. Bald Eagles and Canada Geese are examples. An example of the opposite case is possibly Northern Harriers. The genders have very different plumage, and the male contributes to feeding his offspring, but I think they’re polygamous.
That is a very interesting finding, as is Ben’s on the differences in male/female coloring.
There is also advantage or disadvantage for a few species when you move on to the humans who hunt some of these animals. With pheasants the additional bad news for the male is that he becomes the hunted. At least in some states you can only shoot the male/roosters. They can’t do this with the Canadian Goose.
I have a modified version of that law. If both sexes of birds are similar and brightly colored, then they are monogamous and mate for life.
I think lots of non-monogamous birds have similar-colored sexes: sparrows, shorebirds, swallows? I am not sure they are not monogamous, but I think most of these are not.
Interesting!
Do the gaudy colors make would be adulterers more obvious, then?
I’m excited to hear these 4 laws as chosen by @evolutionistrue; but if “usually”, “often”, or “almost invariably” are the criteria for a law then we could add dozens (maybe hundreds?) more to this list. From basic things like transitions occurring faster than transversions, to more complex things like the inevitable accumulation of deleterious recessive alleles in diploid, sexually reproducing populations.
Indeed. That the probability that a neutral allele will become fixed in the population is it’s frequency in the population (that is, it’s rate of introduction), or the extremely general law that all multi-cellular organisms share one or more common ancestors. 😉
I propose biologists should call this the “slap it on the table” rule.
Sub
Can someone please solve the “Sub” mystery for me? It drives me crazy. What does it mean when someone comments “sub”? Help!
Sub means subscribe. When you place a comment and use the check box underneath, you receive an email for every comment made.
This baffled me at first. You have to post some and check that little box asking for email notifications. “Sub” is presumably short for “subscribe”, but any nonempty text will work. Just remember to check the box!
“some” => “something”.
Remember to proofread!
For ages I thought it meant that the person had commented below somewhere. Then I thought that so odd – why comment that you commented below when you could just comment. Yeah, I obviously over-analyze things sometimes.
What is the reason for the X chromosome tending to evolve faster? Is that also related to sexual selection?
One possibility is that if advantageous genes tend to be recessive on average, they will evolve faster on the X chromosome because their advantage will still be expressed in the hemizygous (XY) sex if the Y, as is often the case, doesn’t contain many genes, and no alleles for those on the X.
Then again, there are reasons why the X chromosome should evolve more slowly than an autosome. Since there are many more cell divisions in the male germ line than the female (in most species, at least), there are also more mutations in the male line. Autosomes spend 1/2 their time in males, but X chromosomes spend only 1/3 their time in males. Y chromosomes spend all their time in males and should be fastest of all.
Of course, that’s neutral evolution, while Jerry is talking about evolution under selection.
I give lectures to medical students on a variety of neuroanatomy, neurophysiology, and embryology topics, and because of my background, often can’t resist the temptation to include the occasional comparative vertebrate biology/evolution angle (not that it would be appropriate to test them on such). One of my lectures is on retinal physiology, and I’ve included some photos of birds, altered to represent what other birds, which possess cones sensitive to UV wavelengths (in addition to some other interesting cone types that mammals don’t have), would see. That makes me think that rule #1 has to be considered in the context of the sensory perceptive capabilities of the species in question (assuming sexual selection is the driving force behind, for example, bird plumage) and/or in the context of the perception of potential predators (e.g. mammalian vs. avian), nest marauders, brood parasites, etc., if cryptic coloration is selected for in female plumage. Related to this, there’s an interesting paper by Stoddard and Prum on “the evolution of the avian plumage color gamut” in a 2011 issue of Behavioral Ecology: doi: 10.1093/beheco/arr088
Does the Hardy–Weinberg principle count as a law?
No, that’s a mathematical consequence of the random combination of genes in a population that’s freely interbreeding and has no migration, etc. If the assumptions hold, the HW equilibrium is reached as a simple result of math.
1a. If a species is dimorphic, it exhibits polygamous mating behavior
I don’t think that has few enough exceptions to make a law. In order to make that into even a majority rule in birds, you would have to enlarge the definition of “polygamous” to include occasional extra-pair copulations. Also, most species are dimorphic to some degree, even if it’s only a fairly small difference in size.
Okay. Lets rephrase it as “The greater the degree of dimorphism (by some measure or index) in a species, the greater the frequency of polygamous mating.”
That’s an interesting hypothesis that ought to be tested. It may be true.
Not related to evolutionary biology, but George Will wrote something good today. I think the Cubs in the playoffs may have affected his brain.
https://www.washingtonpost.com/opinions/a-new-hope-in-space/2015/10/02/5c343cb2-6863-11e5-8325-a42b5a459b1e_story.html
Thanks, nice column.
Confusingly the planet Will uses as an example of interesting things that Hubble has seen was not seen by Hubble but by the Chandra X-ray Observatory. It is notable as being the first time a planet has been detected by an X-ray telescope using the transit method.
Neither Chandra or even Hubble have the capability to reliably image an exo planet. Detection is typically indirect, by an exo planets affects on the parent star, such as variations in brightness when the planet passes in front of the star (extremely tiny) or wobbles in the spectrum of the star caused by gravitational interactions with the planet (also extremely tiny).
About 20 exo planets have been directly imaged so far and all of those, with one exception, were imaged by very large ground based telescopes like the ESA’s VLT at Paranal, Keck and Gemini. The one exception was the famous, and beatiful, image of Fomalhaut b by Hubble.
How about Cope’s rule? It states that within a given animal lineage, body size will increase over time.
And since it applies to macroevolutionary time scales, there’s a lot of work on figuring out microevolutionary mechanisms behind it.
Then why not Allen’s, Bergman’s, and Gloger’s, too? Perhaps these are all more generalizations than laws…
The rules you’ve mentioned (plus Lack’s cluth size) always struck me as ecological rules; they infer some unifying principle based on current ecological distributions. But on the other hand, there’s a very thin line between ecology and evolution, so you might have a point.
As do you. 🙂
Dollo’s law?
Dollo (and correct me if I am wrong) was a Lamarckist and proposed the law (so I am led to believe) as a consequence of unidirectional improvement. The idea was proposed in the 1890s and can have nothing to do with Mendelian genetics or repeating sequences of DNA. I might suggest that given appropriate environments and enough time, penguins could evolve to fly as well as their ancestors could.
Sorry but I am coyning it the law of evolution by means of natural seclection. Don’t we have more than three billion years worth of evidence that all living organisms evolved. And the evidence keeps coming in. That has to be as strong as the law of gravity, law of electrostatics, law of magnetism, law of conservation of mass and energy…
Well there is Poe’s law. It does not, strictly speaking, apply to evolutionary biology but quite often it is invoked in on-line forums about evolution.
Thankfully not often here on WEIT.
One pattern that is generally true but, like Jerry’s four “laws,” isn’t completely understood, is this: species with bigger population sizes have more genetic diversity than species with smaller population sizes, but the difference isn’t nearly as big as the neutral theory predicts. One of Kimura’s equations predicts that diversity should be approximately proportional to effective population size (until population size gets so large that diversity is essentially saturated), so if one species has a population size 10 times as large as another, it should have 10 times the diversity. That isn’t what we see.
So continental species of insects (like Drosophila melanogaster, D. simulans and D. yakuba) should have a LOT more diversity than island species like D. sechellia, D. mauritiana and D. santomea; the continental species probably have population sizes that are hundreds to thousands of times bigger than the island species. Oysters, with census population sizes in the tens of billions (with a “b”, as in “billion”), should be saturated with variation. But while continental species do have generally higher diversity than related island species, they don’t have diversity that is hundreds or thousands of times as big. And species with huge population sizes, like oysters, aren’t saturated with variation; there seems to be a maximum of around 10% (meaning in a random pair of chromosomes, the noncoding DNA will differ at about 10% of sites).
This problem was well known during the height of the allozyme era, in the 1970s; there’s a famous graph by Eviatar Nevo showing how poorly allozyme heterozygosity fit the predictions of the neutral model. People lost interest for a while, but there have been a couple of recent papers on the question of why species with really big population sizes aren’t saturated with variation in their non-coding, presumably neutral DNA.
Possible explanations for limiting factors on diversity include effective population sizes being MUCH smaller than census sizes; selective sweeps; background selection; and mildly deleterious selection against new variants. One intriguing possibility is that there’s an upper limit to DNA diversity in diploids, that if the two homologous chromosomes in an individual are too divergent, they won’t pair properly during meiosis or DNA damage repair.
Whoa! This is really interesting. Can you recommend some articles/reviews on this topic?
Here’s a couple of recent references to get you started:
Molecular hyperdiversity and evolution in very large populations
By: Cutter, Asher D.; Jovelin, Richard; Dey, Alivia
MOLECULAR ECOLOGY Volume: 22 Issue: 8 Pages: 2074-2095 Published: APR 2013
<a href="http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001388"Revisiting an Old Riddle: What Determines Genetic Diversity Levels within Species?
By: Leffler, Ellen M.; Bullaughey, Kevin; Matute, Daniel R.; et al.
PLOS BIOLOGY Volume: 10 Issue: 9 Article Number: e1001388 Published: SEP 2012
Sorry, broken link; that should be http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001388
Thanks a lot!
Very interesting!!!
Nice info. Thx.
How do age of species since time of divergence, and geographic distribution, as distinct from size of population, relate to genetic diversity?
That is interesting. I was starting to think of possible solutions, but you brought them up in the last paragraph. Those explanations should be testable and that what science is all about.
There’s a rule in avian reproductive biology noted by David Lack: increased clutch size with increasing latitude. There are a few exceptions that have been described, but in general it holds true as it’s related to multiple factors (resource availability, day length, nest predation, seasonality, and egg viability due to high temperatures).
I’m confused. Shouldn’t that be “increased clutch size with decreasing latitude”? If not, I’m missing something.
Nope – among and within species, clutch sizes are larger in northern temperate latitudes than in the tropics closer to the equator. The Cesspit of Lies is actually pretty good on this one: https://en.wikipedia.org/wiki/Avian_clutch_size
Wow. I would have thought the opposite! Cool. I suppose penguins are one of the exceptions.
They are southern
Doesn’t latitude increase in the southern hemisphere, too?
“Cesspit of Lies”! Hadn’t heard that one before.
Sub
Have there been any ‘patterns or generalizations’ which have ‘become sufficiently general and impressive’ in the area of Evolutionary Psychology?
This is one area to which I have paid little attention so this question may be naive.
The emphasis on patterns is so important. Not one single creationist I’ve ever talked to understands this. They all have their pet fact – “yeah but what about this that happens every seventeenth year in the Peruvian Andes when the moonlight lands just right? – and just gloss over when I explain that evolution is not a handful of facts but a description of patterns and observation found in nature. Certainly there are facts but eXceptions only prove how messy biology and evolution and life can be. If you don’t like messy be an engineer where everything comes to a yes or no.
Reblogged this on Monkey Dance and commented:
Fun conversation about the messy rules – patterns really – of evolutionary biology. Check it out for a good read.
Isn’t there some kind of widely observed principle that on islands small animals become bigger and big animals become smaller?
That’s how you end up with with pygmy hippos and Sumatran leopards, large critters that are smaller than their mainland relatives. And you also get Komodo dragons and the now-extinct moa. Much bigger than their mainland kin.
I seem to recall this idea had a name.
Foster’s rule I think.
Thanks. Google confirms this.
I don’t have a law, but I could suggest a Bill Maher-style New Rule:
Anyone who tells Richard Dawkins that he’s too strident and shouldn’t hit people over the head with science, has to listen to that hour-long interview he did with Wendy Wright the creationist.
Yowza, when I last saw that she had me yelling at my computer monitor after just a few minutes. Richard deserves an award for patience for that one.
There’s Allen’s Rule but it isn’t a law. I learned it many years ago in Anthropology and for some reason never forgot it.
Allen’s Rule is as much of a “law” or “principle” as any. In homeotherms, when there is cold stress or heat stress, selection will tend to favor reduction or increase, respectively, in body area. If selection has not made this happened, it should be possible to identify the constraints responsible.
Bergmann’s Rule of increasing body mass in homeotherms in high latitudes (decreasing temperature) should also count, but again, there are constraints, and it does not always apply. The rate of falling of feathers is also varaible, but this does not invalidate the law of gravity.
There is an “anti-Bergman” rule in insects with yearly life-cycles: high latitude populations seem to have smaller individuals than in warmer clines. This is because the growing season is shorter near the poles and there is less time for, say, a grasshopper to grow big.
It seems the rules reinforce, at a fundamental level the need for information preservation. But why?
It is as if life is intrinsically self-interested in itself. Preserving itself simply because it (life) finds itself worth preserving. Humans are only different in that they are aware of this process. It seems that it is a cycle that would never not dominate a planet and possibly as many planets as possible given enough time.
I guess the simplistic answer is why not? Once self replicating, populations will survive in sufficiently slowly changing environments by the dumb evolution process. (No time travel to peek at future solutions. “Dumb process!”)
The process ascertains that it is selfish, because immortal cells would have to be infinitely capable of lamarckian evolution to survive in a competition.
But there are also attempts to base life in self organizing, self sustaining, self replicating thermodynamic systems. Engaging as they may be, they seem to me to attempt too much vs Dawkins’s selfish genes.
FWIW, law 3 seems based in law 4 to me. My feeling is that those would be lumped together into one law in other fields. But I don’t know of course.
The history of “laws” in physics has, as usual, made a mess of any generic attempt at defining them. Newton’s laws are part of classical mechanics, and as such they can be seen as consequences of action, a quantity that embodies conservation laws. And that is now understood as more fundamental laws based on symmetries.
At the same time there is a lot of pattern laws in more applied fields, like Arrhenius law (equation). And of course the whole concept has become a bit outdated, there is a lot of later similar relations that are called something else. (Einstein’s relationships between diffusion and mobility in semiconductors, which holds for small currents, comes to mind.)
gluonspring mentioned common ancestry as law. I think we can go further, in analogy of how stars starts out as mostly hydrogen based on initial conditions in mixed molecular clouds – a universal pattern – we can claim laws due to common ancestry:
– Organisms are cellular. (Cell theory.)
– Modern organisms are DNA based.
– Modern Earth life has a universal common ancestor lineage.
– Cells use chemiosmosis.
… et cetera
Let me promote one of Jerry’s responses.
[On the Hardy–Weinberg principle:] “No, that’s a mathematical consequence of the random combination of genes in a population that’s freely interbreeding and has no migration, etc. If the assumptions hold, the HW equilibrium is reached as a simple result of math.”
I have seen this argument before, and I don’t fully get it.
It is a non-trivial universal pattern that is the result of reaching an equilibrium in certain situations. As a comparison, entropy is a useful universal pattern that is the result of reaching a thermodynamic equilibrium in certain situations. It is no less a mathematical consequence of the random combination of particles in statistical physics under certain assumptions (such as equal prior probabilities). And thus we have the 2nd law of thermodynamics.
Maybe I am influenced by someone asking for biological laws once (I forgo where), and the response was my first introduction to HW. “The Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law, …” [ https://en.wikipedia.org/wiki/Hardy%E2%80%93Weinberg_principle ]
I get that there is no analogy between the TD and HW equilibriums in the sense that the TD equilibrium is often reached by forcing, while the HW equilibrium is a fixed point of gene frequencies. (I.e. once in a HW equilibrium the gene frequencies stay the same until something changes them.) But fixed points have interesting consequences, at least in physics. [ https://en.wikipedia.org/wiki/Fixed_point_(mathematics) ]
So I guess YMMV, especially for a layman bystander that try to grok the field. If it is a reminder that there is no forcing in the system it may make sense to not put it on a list of biological laws. If it is forgetting that it is a universal pattern of systems that have folded phase spaces (here no new alleles, no new ways to combine them in such as a 3d sex), and that it is describing something interesting, it may make less sense not including it.
I thought something similar when I read that. I suspect that ALL the laws and regularities of biology at a given level are in fact mathematical consequences of more fundamental factors.
It’s interesting that none of the laws are specifically about the evolution of adaptations in response to variation in the environment or the conditions of life (1. and 2. are arguably about male adaptations to the other sex). Does this reflect a lack of regularity in which adaptations will arise (unlike the regularity in which sex will evolve ornaments, or show rapid evolution of genitalia, or experience hybrid sterility)? Are adaptations to the conditions of life so contingent on history and circumstances that they are not predictable enough to form the basis for laws? There are generalizations like Cope’s rule, but imho these are interesting mainly because they are so often violated. I’m not criticizing Jerry’s choice of laws, just observing the types of evolutionary ‘products’ to which they seem to apply (or not).
What about “Use it or lose it”?
I like that.
I lost my appendix last year. Haven’t missed it yet.
Give it geologic time.
Tough–but I’ll give it a try. 😀
This seems like the opportune occasion to quote this recent article:
“Spider has sex, then chews off own genitals”
https://www.newscientist.com/article/dn26812-zoologger-spider-has-sex-then-chews-off-own-genitals/
Includes the lovely statement “But then, she does try to eat the male, so a lasting relationship is hardly the first thing on either spider’s mind.”
cr
Reblogged this on Nina's Soap Bubble Box and commented:
YES! steps and stages – puncutated
The Eternal Question – Chicken or the Egg?
Eggs because there were already egg laying species is the pedantic response
but it was Something Not a Chicken that Laid an Egg with a chicken in it – and it was not discouraged, disfavoured and over time, more becomes a population and breaks off from the original source and POOF Chickens
Jerry, your four laws are valid for (most) animals, that is for individual organisms with separate sexes determined by heterochromosomes.
But animal sex can also be determined by temperature (Crocodilians) or age (Crepidula fornicata, a marine Gasteropod), large groups of animal species are hermaphrodite (e.g. Pulmonate snails), like most plants (but at least some dioecious plants have sex chromosomes) and fungi can have more than two “sexes”…
Yes, I thought it was implicit in the rule itself that this holds only for animals with distinct sex chromosomes (and mostly those in which one of the chromosomes in the heterogametic sex is genetically depauperate, like the Y in humans.
5. Survival of the species takes precedent over survival of the individual. (A plant or animal will die in the effort to reproduce; an individual will die to save others in the tribe, herd or flock– altruism.)
No no no…..
Inclusive fitness leads to some similar “laws”, but to my knowledge no animal normally sacrifices itself to help individuals that are unrelated or distantly related to itself. In fact, I propose that this, the opposite of your rule, is a good candidate for a nearly universal rule in evolutionary biology.
Actually…we see that relatively often. Just look at all the cute YouTube videos of, for example, mother cats who’ve adopted orphaned ducklings or squirrels. And, of course, humans are well known for sacrifice in all sorts of circumstances.
The key, of course, is that the recipient of the altruistic sacrifice is, at some level, perceived as being sufficiently closely related. The cat mistrakes the orphaned prey species for one of her own kittens, human soldiers defend the lives of their brothers-in-arms, and so on.
Evolution isn’t perfect, just perfecting.
Cheers,
b&
Yes, that’s why I included the qualifier “normally”. Altruism towards unrelated, non-reciprocating individuals is a strategy that would not increase in a population. All the examples you mention are taken out of the context in which those behaviors evolved.
“… because we sure as hell can’t trust the cops”.
Sorry, instinctive cynical reaction.
cr
Damn, wrong thread. Can’t trust my browser either. Please ignore.
cr
Why are some clades male-heterogametic and others female-heterogametic? Is there an understood mechanism for ‘switching’?
I mean to ask ‘how’ rather than ‘why’.
A couple of rough ideas (might be garbled, or “not even wrong”).
“Law” like quotes, some borderline tautological, or obvious, but maybe it gives somebody an idea…
A couple on kin selection:
There are probably a couple of more that are generalizations, like the various “rules” that can be deduced once a species looks like a tournament, or pair-bonding species (levels of aggression, dimorphism, high reproductive variability)
Another false friend… bee hive (I knew it! they still sneak in sometimes).
I would prefer to not call these things ‘laws’ since such complex and nuanced things as evolving populations are fraught with caveats and special conditions. Still, using the term law for the moment:
I would suggest a law or two about speciation. One law is that speciation can happen when one population in some way becomes reproductively isolated from another population. Over time, if evolutionary changes that differ between the two populations include incursions into matters of mate choice and/or fitness of hybrids, then we can say that speciation is occurring.
I agree, that seems like a good candidate. Although I think something like “gene flow between populations ceases” might be slightly better, more general. But that is nitpicking.
Hamilton’s Rule? rb > c
THANK you, Jerry!
“Generalization” is fine with me, in the sense elucidated by Coyne:
‘“laws of evolutionary biology”: those generalizations which hold sufficiently strongly that explaining them in one group might also give explanations for all groups.’
I will again suggest that what I have suggested many times in the past will pass the test, and add the suggestion that it is not a “not-law” until a case or an example can be shown or cited that honestly contradicts it or is inconsistent with it:
“All organisms do what they can, when they can, where they can.”
Best,
Wayne Tyson
PS: We are, after all, trying to describe a complex phenomenon with words and language, and all the tangled webs that that entails. Despite repeated examples to the contrary, the quest for understanding the IS is, is not at all about who’s on first, second, or home, or even who’s right–it’s about, as Jerry and Richard (Feynman) have said, “the pleasure of finding things out.” Even if they are wrong–all conclusions are provisional in science, no?
Certainly one such “law” is the extraordinary conservation of genetic and developmental software in contrast to plasticity of body plans and structures — the “endless forms most extraordinary” of living organisms.
Examples include the “central dogma” and doing of proteins, HOX genes, genes involved in building eyes..
I doubt that this would have been predicted a priori.
That photo of Haldane was used as the cover of a book I read recently, and which has been taken from the rig library and so is probably being read by someone else.
Top man, Haldane. Amongst other things, he broke bones in his back (to the point of back pain, not permanent paralysis) studying the dose at which oxygen becomes a convulsive poison in humans.
To my surprise, the safety ossifer and former diving life-support technician at the desk behind me, hadn’t heard of Haldane. There’s something wrong with diving LST training, I fear.
The first pattern that attests to the validity of the first of “Kohl’s Laws of Biology” is that all living genera must eat to reproduce. Thermodynamic cycles of protein biosynthesis and degradation link the epigenetic landscape to the physical landscape of DNA in all living genera.
No organism that has ever contributed to the earth’s biomass appears to have automagically evolved, which makes all the claims of evolutionary theorists appear to be absurd.
However, keep in mind that the works of this year’s Nobel Laureates in Medicine will continue to force all theorists to reassert their ridiculous claims or abandon them before the evolution industry implodes and big bang cosmology industry implodes, and both return to their origins in lawlessness with patterns.
Re: Lawlessness with patterns.
See also: “In other words, genomic conservation and constraint-breaking mutation is the ultimate source of all biological innovations and the enormous amount of biodiversity in this world. In this view of evolution there is no need of considering teleological elements” (p. 199).
http://www.amazon.com/books/dp/0199661731
Nei also removed “natural selection” from mutation-driven evolution, leaving only the pseudoscientific nonsense. No explanatory power. Mutations-driven evolution happens automagically. In his “…view of evolution there is no need of considering teleological elements”
In my view a scientific law just *is* the objective pattern in nature or society. A scientific law *statement* is the way we say or write our conceptualization of the pattern in question. So of course there are lots of laws in biology. However, what is interesting is trying to find *statements* that are appropriately illuminating and can be appropriately interlated.
I would include something like “evolution is cumulative” – something the old “nature does not make leaps”, but with appropriate grasp of genetics, etc. Hard, but maybe a project for someone. 🙂
I’d just add that the “laws” of physics are not different in kind at all. They are also just observed patterns and regularities in the “behaviors” of particles or fields. There are just far fewer variables involved, making the regularities considerably less messy.
“There are no “laws” in evolutionary biology comparable to those in physics”…
Is not Natural Selection a law of evolutionary biology?
Forgive my terseness, and I don’t mean to JAQoff.
I think that if you can a give phenomena a mathmatical equation, such as E=MC^2 or F=ma or whatever then it indeed a law.
Now quantum mechanics deals with uncertainty and probabilities a lot, which makes the maths much longer and harder to understand.
But just because the equation for the standard model of particle physics will fill an a4 sheet of paper, doesn’t make it any less of a law.
Surely there is similar long convulted mathematical equation for Natural Selection?
Laws? There are also apt wisecracks.
Bussing’s (William A., late ichthyologist) wisecrack: Isolation makes variation. So what?