I give my undergraduate evolution class this example of the differences in reproductive potential between human males and females—a difference seen in many animal species, and one that’s certainly the physiological basis for sexual selection and sexual dimorphism (the difference in appearance or behavior between males and females of a species).
I found these data in the Guinness Book of World Records years ago, but they’re confirmed by a fascinating site on human reproductive records that bears some perusal.
Most natural children born by a woman. I always have my students guess this, and they always guess way too low:
One of the most stunning records in history can go to one very fertile Russian woman who gave natural birth to sixty nine children without the use of fertility aids! The children were all born between 1725-1765. In twenty-seven pregnancies Mrs. Vassilet gave birth to sixteen sets of twins, seven sets of triplets, and four sets of quadruplets. Only two of these children died in infancy, a staggering statistic by itself considering the day and age!
I weep for this poor woman: imagine having that many mouths to feed! Granted, the oldest was already forty when the youngest was born, but that’s still a lot of people at table. Mrs. Vassilet obviously had some genetic or developmental condition predisposing her to multiple births.
In contrast, males can have many more offspring, since they’re not limited by pregnancies or the impediment of fertility caused by lactation.
Most offspring sired by one human male. There are reports that exceed these data (Genghis Khan and so forth), but they’re less reliable; Guinness, I think, goes to some trouble to verify its records:
Of course sixty-nine children by one mother is absolutely astonishing but what kind of family could a man have with no less than five hundred wives? Historians think Mulai Ismail sired somewhere around eight hundred children sometime in his life between 1646-1727 where he ruled as the last Sharifian Emperor of Morocco.
As expected, a man with having many offspring was a man of considerable status.
The more than eleven-fold difference in reproductive output at the tails shows the vastly greater number of children potentially produced by males versus females. And that is why, evolutionary biologists think, in most animal species males must compete for females. With a limited number of offspring in their lives, females must be choosy about their mates, while males, for whom reproduction is far less costly (just a teaspoon of sperm in our species), will mate with nearly anything.
This is also true of my fruit flies: females will repeatedly reject the ministration of males, and the males will try to mate with anything, including other males, blobs of wax, or tiny dustballs! Psychology experiments in humans repeatedly show that women are far less willing than males to mate with someone whom they don’t know well.
And that’s why, when only one sex in an animal species has ornaments, plumes, or elaborate calls, it’s nearly always the males. Think of birds, for example. Dimorphisms are also seen for weapons like horns or antlers, which in males are larger because they’re used in male-male battles involving competition for females.
The male bias in sexual ornamentation is one of what I consider three “laws” of evolutionary biology: generalizations that are almost without exception. Can you guess the others?
What are the other two laws?
Never start a land war in Asia, and never make a bet with a Sicilian when death is on the line.
You mean never try to take Asia in the game of Risk?
Always try to take Asia in a game of Risk, but only once you’ve got the Australian continent (for it’s troops boost), a heavily-defended Vietnam / Indonesia (to deny anyone else the boost of having all of Asia), and try to maintain footholds in all the other continents (which typically means that you want to hold Iceland in Europe and Greenland in North America, de-monopolising two continents and controlling an invasion route). After that, as long as you can stop anyone else from getting South America or Africa, you’ll eventually get enough troops to roll back the rest of your enemies through Asia.
+1. The Princess Bride.
Inconceivable!
/@
We are men of action, lies do not become us.
Oops. Didn’t see the part where you ask us to guess the other two laws.
Let’s see . . .
Perhaps another concerns the differential reproductive success of asexual vs sexual reproduction, with asexual being favored in changing environments? Although I understand that it’s not completely clear why sexual reproduction is beneficial.
Sex ratios always honing in on 1:1, males:females?
That Russian woman was fertile for 40 years in a time when people didn’t grow as old as nowadays? =\
That Russian woman survived 27 pregnancies in a time without modern medicine where childbirth was a very risky proposition.
The guy with 800 kids is mildly impressive from a time management standpoint (where did he find the time to do much of anything other than siring children?), but Mrs. Vassilet is someone who needed to hit the craps tables with a string of luck like that.
With 500 wives you can have 800 children easily in 2 years. Copulate with 2 wives each day, and you’ll impregnate all your wives in just 250 days (less than 9 months). Wait for the 300 of them to wean their children next year and impregnate them again.
This assumes perfect record of impregnation per copulation. You can halve the success rate and still produce 800 in quick time.
No problem with time management at all.
That is only assuming a rather spectacular rate of success. A woman is only fertile for a few days per month, that works out to less than 10% of the time, and even when fertile copulation doesn’t always lead to fertilization and up to 80% of fertilized eggs are spontaneously aborted (or never implant in the first place).
Oh certainly if you have sex with 2 wives every day and rotate evenly between them then you will have sex with every wife every 250 days but chances are that isn’t even how the rotation went since he probably didn’t marry all 500 at once but started out with much fewer before becoming emperor. However going with the 2 per day (quite ambitious when also running an empire but not out of the realm of possibility) with typical fertility rates then 800 children would easily be possible in a couple decades.
The average age people live to has mostly increased due to the reduction in infant mortality. People only lived shorter on average before due to all the untimely deaths before antibiotics, dying in child birth etc. If more people die young, it pulls the average down, even though those who do escape such ills will live the traditional “fourscore and ten” years. The underlying lifespan of the human being hasn’t changed much. It’s a common misunderstanding.
Okay, it doesn’t undermine your main point, but I’m going to express some skepticism here, since 18th century Russia probably wasn’t a model of modern science and record-keeping. This sounds like anecdote bolstered by someone important writing it down.
My own sly guess is that –assuming it’s not outright fabrication — there were several members or generations of a family where the women could (and would) pass with outsiders as a single person.
Look. What does Snopes say?
Snopes doesn’t hit for “Feodor Vassilyev” (the woman in question only ever being described as “the wife of Feodor Vassilyev”).
Many doubts have been raised about this claim. The Wikipedia article discusses some.
Sign Mrs. Vassilet up to be a poster child for the Republican party…
Somewhat appropos your photo at the end:
http://www.eurekalert.org/pub_releases/2012-06/uoc–ubr062512.php
(“UCLA biologists reveal potential ‘fatal flaw’ in iconic sexual selection study”)
Just saw it and haven’t looked at the details yet.
“And that is why, evolutionary biologists think, in most animal species males must compete for females. With a limited number of offspring in their lives, females must be choosy about their mates, while males, for whom reproduction is far less costly (just a teaspoon of sperm in our species), will mate with nearly anything.”
Following up on that, Darwin was, I understand somewhat puzzled by the apparent competition for males among human females –beauty treatment, clothing (or lack), cosmetics etc. What appears to be happening here is not a reversal of competition, but a second competition. The male competition for females is still fully in place, but with the human development of long term mating to support the extreme resource needs of human young, there is a competition for reliable males, and here the ratio is reversed. There are plenty of males out there but not all of them are suitable long term partners. Females are competing not for just any male (that’s usually not much of a problem) but of one that provides potential resources for the young. And this second competition can be as intense as the first.
Reblogged this on itaatee.
Perhaps another “law” would be that species isolated on islands become smaller than their continental cousins. Like mini-mammoths on islands in the Aleutians. Or was it islands off Siberia?
But some animals become gigantic on islands, like komodo dragons, elephant birds, giant tortoises, etc. The rule seems to more be that large species become smaller and small species become larger on islands.
And Do Dos, they were giant pigeons.
Too bad this argument is wrong.
The crux is that selection acts on *average* reproductive rate – not potential reproductive rate.
Queller showed this in 1997. If you have about equal numbers of reproductive males and females (which you normally do because Fisher’s principle) then average reproductive success is the same.
A problem with earlier models is that they assumed an infinite sea of females for males to mate with.
A more tenable explanation is paternal uncertainty, which, as a bonus, helps explain higher paternal care in most fishes.
Here is a short review:
http://www.anu.edu.au/BoZo/kokko/Publ/index.html
Better link:
http://www.anu.edu.au/BoZo/kokko/Publ/Tango.pdf
Sorry, but I don’t agree with you. First, Queller’s article is about parental care, not sexual dimorphism in ornaments or weapons that attract mates, and second, he says that the argument based on mating potential for parental care is “not wrong, just incomplete.” As far as I can see, the argument for sexual selection based on different contributions to offspring (ultimately resting on gamete dimorphism and the higher variation in male reproductive success), is still correct. And there are tons of species without parental care, including fruit flies, and they still have sexual dimorphism, so “paternal uncertainty” is not an issue.
Indeed in many of the most sexually dimorphic birds in South America (like the Cock of the Rock, and the manakins) the males offer no parental care at all.
In addition I believe the pattern is that the more equal parental investment and care is, the less dimorphism is expected and observed.
Points taken. My mistake.
And this, folks, is why science wins over theology. When is the last time you’ve heard a church look on its doctrines, nod its collective head in response to criticism, and say, “Point taken. Our mistake.”
First, you don’t always have equal numbers of males and females. You have equal investment in males and females, which is not the same thing, and is in fact what Fisher suggested.
Second, given equal numbers of males and females, average reproductive success will be equal by definition. That’s not saying anything interesting. Median success, however, is something else entirely. Each successful reproduction will have behind it one female and one male. The number that any single female can claim credit for will be constrained by the speed of the actual reproductive act. Not so for males, who need invest nothing but a few cells which they can produce daily in the millions. It is therefore not uncommon for hosts of males to have no success at all, while others whittle away the bedposts to nothing with all the notches. That pushes the median success for males well above the median success of females, which squares perfectly with the point made by this website post.
Though I wouldn’t really put it that way myself. I see greater median reproductive success as a consequence of the real issue, which is resource investment. As soon as sexes began to differentiate, with one becoming gene receptor, and one gene donor, the road to male competition was laid out (where male is defined as the sex that donates genes, in a small inexpensive package).
In a distribution with positive skew (i.e. a small percentage with high success rate), the median is below the mean. That is, the median success will be lower for males than females, given that the mean must be equal.
In fact, if less than half of the males are reproducing (which happens in many species), the median for the males will be zero. But I think it’s the standard deviation, not the median or mean, that matters.
Other “laws” of evolution biology. Okay. Hmm.
–The ones with the sharp teeth are usually the meat-eaters.
–Bright colors mean either “I’m poisonous” or “Neener-neener, you can’t catch me!”
–The number of offspring produced is inversely proportional to the degree of parental care invested.
Hmm. This is hard.
I remember reading the same facts about human reproduction in my intro anthropology class at UConn. I couldn’t remember the exact number until I read it here, but I knew it was mostly multiples. It’s staggering to think of that many kids simultaneously!
Ugh. It was my distinct displeasure to interact with a “quiverful” family recently.
The mom was fracking exhausted. The dad — oblivious.
The kids were nice enough — they were in that “cute” age. 8 of them under the age of 12. In other words, pre-teen-rebellion.
I have a Mormon colleague who seems to be trying to go after that guy’s record.
I exaggerate. But he has more than enough to field a baseball team.
The other two laws, I’m guessing, have to do with arms races, and plant-shape/pollinator…..
In that, for example, the cheetah and antelope species, will continue in their arms race…as the antelope gets swifter and more agile, the cheetah gets that much faster….
And that if a plant has a longish or elaborate tube design leading to its nectar, there is bound to be a pollinator species that is specifically adapted to it.
Was i at least close?
more laws:
-Death
-Genetic Drift
-Differential survival of replicating information.
-Adaptation
-Parasitism
-Crick’s central ‘dogma’
How’s about:
in species with pair-bonding or other kinds of restriction as to which males get to mate (such as territoriality), the sperm volume produced will be less than that in species where the females mate with multiple males
(that is, there will be selection advantage to large volume sperm production to wash away competitors’ sperm if it might be there–pair bonding means it won’t be there in the first place so there wouldn’t be pressure to up the amount)
Yes– bigger testes indicate females mating with multiple partners (sperm competition).
I don’t know if the size of testicles is the relevant feature. I can only vaguely recall a study done, wherein sperm production was measured in males when females they interacted with sexually, were in environments where male competition (mating) was possible.
This led to increased sperm production in the males. The conclusion, from an evolutionary perspective humans a not a monogamous species. We are adapted to be polygamous.
This pretty much only applies to ducks, though:
If your penis is shaped like a corkscrew, your potential mates’ vaginas are too.
And opossums, too, altho with a different shape (they’re bifurcate).
I always wonder how those bifurcate penises work… I’m not sure I really want to know, but it is a strange set up. The echidna penis has four “prongs” (dongs?) like a fork.
I think I recall pigs have the corkscrew too. At least I think I learned that in an animal science class once–the odor of the pig barn made it hard to concentrate! I had to leave my clothes outside after coming home from class that day.
I believe there is some debate about whether Moulay Abdul Ismail the Bloodthirsty could have managed that amount of impregnation, but he did apparently have a rather battery farm approach to his harem – members in young and fertile, out with a full pension while still in their twenties and a close account kept of menses. There is a paper that discusses it – I shall look for link. He is an interesting character in other ways, being a great builder of palaces in Morocco, some of which still stand in part, and an active slave trader, sending ships to raid even western Britain, landing in Cornwall and carrying off thousands of Xtian slaves. “White Gold” by Giles Milton tells of this bit of history.
Here’s a thought. Sexual dimorphism is thought to arise is an honest signalling mechanism allowing the female to really assess a potential suitor’s fitness. The peacock’s flamboyant tail says “Look, I am so egregiously fit, I can survive even with this obvious handicap on my backend.”
I think it might arise as a way for the female to even the odds against the potentially prolific males. She selects for an impediment that results in the early demise of the male so that her brood has a better chance to survive without the philandering male overpopulating her environment. Monogamous species don’t select for handicaps because the females rely on the males for chick rearing.
The degree of dimorphism in birds seems to coorelates well with the degree of paternal investment. The male “goes along” with it because he has to (short of coersion) and because his inclusive fitness improves by not being able to overpopulate his environment with too many chicks.
You may not realize it, but you appear to be making a group selection argument. Jerry won’t like it. You have females choosing males of lower current fitness; genes that cause such things to happen will decrease in frequency in a population, even if populations that practice this odd form of population control are more successful.
Now if we’re talking about individual selection, a handicap only works as a signal if the cost to a high-quality male is less than the cost to a low-quality male.
Further, a female shouldn’t care to even the odds. She isn’t competing with males for offspring. She’s competing, if anything, with other females. She doesn’t care who else the male who mates with her also mates with (assuming parental care isn’t involved). She just wants to mate with the best available male.
Thanks for the excellent feedback! I don’t think it’s a group selection arguement though; selection at the level of the individual hen favors those hens that choose mates with longer tails. If the cock is not going to aid in child rearing, there is no question the hen would be better off with him dead. It reduces population pressure for her brood. She is simply more subtle than the praying mantis or black widow spider who kills her mate outright.
I don’t think you have it quite right for this reason:
Her male chicks will each carry as much of her genetics as her female chicks. If they “live long and prosper”, each fathering a gazillion little ones, she benefits greatly. The genes for fancy-looking males will propagate to the extent that they increase her offspring’s offspring. Her interest would be if all the other (non-dad) males were to die off, but not for her mate to die off early.
“She selects for an impediment that results in the early demise of the male so that her brood has a better chance to survive without the philandering male overpopulating her environment.”
Besides the fact that hens don’t have the cranial capacity to entertain such thoughts, I don’t see how this makes any sense. The male already has its genes. She is completely incapable of selecting what genes he has. All she can do is select what genes her children have. How is having children that die young good for her? You seem to be unclear on evolution, the arrow of time, or both. If females hens prefer males that die young, that will cause genes that cause males to die young to be prevalent in FUTURE generations. But you’re arguing that it benefits the hen if males from PREVIOUS generations die young. Unless the hen both has a time machine and the cognitive reasoning skills to comprehend your argument, I don’t see how this isn’t nonsensical.
I think that your hypothesis is symptomatic of a deep confusion among lay people regarding evolution. While evolutionary principles are often presented in teleological form, they are so presented with the understanding that the teleological language is shorthand for blind natural forces. Hens don’t actually care about the reproductive fitness of their mates; they are incapable of formulating the concept of “reproductive fitness”, let alone consciously deciding to mate with males that exhibit high values of it. The don’t realize that particular mating strategies will benefit them, and then “decide” to follow them. Rather, those who follow beneficial strategies have their genes propagated at a superior rate, and thus act *as if* they “want” to mate with males with high reproductive fitness. If you have a hypothesis involving animals coming up with some “plan” to have more offspring, and it’s not possible, at the very least in theory, to reword it in terms of natural forces, then it’s just plain wrong. If that’s not one of the laws, it should be.
“The male “goes along” with it because he has to (short of coersion) and because his inclusive fitness improves by not being able to overpopulate his environment with too many chicks.”
Inclusive fitness requires that the direct disadvantages be outweighed by the indirect advantages. The whole dying young thing is such a massive disadvantage that the advantage would have to be even larger.
Evolution is cleaverer than you are!
When a spontaneous process is too slow or too inefficient a protein will evolve to speed it up or make it more efficient.
Did I win? (^^)
Evolution is NOT cleverer than I am. Evolution cheats.
You seem to care about methods ; evolutionary success cares about (well, only consists of) successful results.
Evolution wins.
I don’t like cheats either. Which is why they have backs and I have daggers. That’s cheating too. Meh.
No, evolution is really, really stupid, that’s why it takes so long to get anything done and it is all incremental.
Evolutions Are Stupid (But Work Anyway)
One guess at a “law”
– Some sort of isolation (geographic or otherwise) is required for speciation.
That one has been bust. Or to be more precise, the level of isolation is lower than we conceive (pheromone cues might utterly escape us, for example).
Tough one. One obvious law is:
– Atheists accept evolutionary biology, accommodationists can do anything and no one cares particularly, and creationists r doin’ it rong.
But that last one? Hmm…
No not really. The last one(s) could be Price’s theorem or Fisher’s fundamental theorem.
Diversity (of species, genera, or families) increases toward the equator and decreases toward the poles, even if the number of individuals in a given area is the same.
That was my guess, too.
It isn’t really a “law” because it’s just an observation that applies to the current tectonic and climatic regime – we can’t project it forward into the future or backward into geologic time (not enough information).
It also just occurred to me that “diversity” also applies to genetic variation WITHIN a species, which is dependent on several other factors (number of chromosomes, evolutionary history, etc.).
Is one of the “laws” Haldane’s rule?
“When in the F1 offspring of two different animal races one sex is absent, rare, or sterile, that sex is the heterozygous sex [heterogametic sex].”
Yes!
Translation into lay terms, please? Are we saying, roughly speaking, all mules are males?
Being male doesn’t matter, per se. Being hetergametic (having your sex chromosomes be of a different kind – like XY in humans) is the important part. In birds, the females are heterogametic (ZW), so you’d see Haldane’s rule apply there with females as the “absent, rare, or sterile’ sex.
Whoops, I should’ve wrote “…like XY in human males”. Non-XY people are humans too, Rick Santorum’s opinion notwishstanding.
So if a human mated with a Neandertal, the males would be more likely to be sterile (or absent) than the females. Cool.
A biologist might not hesitate at guessing which pheasant was the male, but an avid birder might have second thoughts. The venerable James Audubon ‘hisself’ was fooled when he assumed, incorrectly as it turned out, that males of the Pharalope family were the gaudy ones. It took some years before the error was discovered (so I’ve read)! Certainly a rare enough exception…
Here’s an article about phalaropes for anyone who is interested:
http://www.birdfellow.com/journal/2009/06/02/role_reversal_a_closer_look_at_wilson_s_phalarope
Of course, “almost without exception” doesn’t mean “without exception”. The two cases in birds in which females are fancier than males — jacanas and phalaropes — are widely known.
Do you know of others? I’d be surprised if there weren’t several in insects, but I don’t know of any.
There are some good ones in insects! Orthopteran males often produce huge gelatinous proteinaceous blobs as part of the spermatophores which are attached externally to the females. These either act as contributions to the provisioning of eggs they fertilise or as ‘sperm guards’ that prevent females removing the sperm-filled part: the females chew on the gluey blob instead. In some bushcrickets this blob and the spermy bit can be up to 40% of his body weight – as a result males can take up to 4 days to recover, while the female can remate in 1-2 days. A 1:1 sex ration means a skewed operational sex ratio and female bushcrickets compete for access to males and males can be fussy about which females they mate with – a neat reversal of Darwin’s ‘ardent’ males and ‘coy’ females.
Isn’t there supposed to be some kind of reproductive records associated with Chengiz Khan and his sons, even to the extent that it can be traced genetically to this day?
I read somewhere that 8% of north Asian men share the same Y chromosome which is assumed to be that of Chengiz Khan.
I know what you mean, but I am still having fits of laughter imagining a bunch of north Asian males trying to grab that one single Y chromosome that they have to share.
My guess for one of two remaining “laws” of evolution is that if one of the sexes of a hybrid is infertile or of reduced viability, it is the heterogamic one.
Yes, correct; that’s “Haldane’s Rule” which I mentioned in a comment above. I spent a lot of my career working on that one.
There’s one rule to go. . .
“Most natural children born by a woman”
I thought they all were. I guess this is why I’m a musician and not a biologist.
the “large X-effect”
the disproportionately large effect of the X chromosome on hybrid sterility and inviability.
Bingo!
So two of only three “laws” in all of evolutionary biology have to do with, basically, the sterility of hybrids? Why such a poverty of laws in such a huge field?
Because anarchy is pretty darn effective, if you don’t count the death and suffering (which nature doesn’t).
Genetics can haz laws (where’s Hardy-Weinberg, JC?), but ecology only has rules (well, guidelines really), and in most of biology we have historically contingent facts, which make wonderfully consistent but not very predictive* patterns in space, time and phylogeny.
*not predicting what will occur in future, but very good at interpolating (predicting what will be found when we look into the gaps) which is epistemologically sufficient for SCIENCE.
Is there any relationship between the large-X effect and Haldane’s rule? This is the first I’ve heard of either of them, but based on the one-sentence summaries that I’ve read, I could believe Haldane’s rule is a consequence of the large-X effect.
So all three laws are about sex. Interesting.
How interesting. I was just trying to mate with a blob of wax the other day…
…
oh
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TMI?
Video, or it didn’t happen!
Would you consider angler fish to be an exception to this law? Or praying mantises?
Not exceptions, because they are not generally dimorphic in ornamentation.
These examples can be pretty extremely dimorphic in morphology and behaviour, though, for reasons that make sense in terms of anisogamy.
This seems like a good opportunity to ask a question that has puzzled me for some time. (It’s certainly not a challenge to evolutionary theory, which everyone here but the occasional troll knows is solidly established at this point.)
Why is it that human females tend to ornament themselves (cosmetics, hairstyling, fashion, foot-injurious shoes, etc.) when no other species seems to have its female members ornamented, except for a few where the male has a disproportionate investment of parental energy (egg nesting fish, as I recall)? It sure doesn’t seem like men worry much about their appearance as much as women do, yet it’s undeniable that sexual selection with female mate choice plays a role in human behavior. And men certainly display their genetic fitness toward the women they hope to impress in many ways, ways that often occasion some
amusement by both men and women nowadays.
So, why, since well before modernity came along and made things like “optimizing reproduction” somewhat academic for most sexually active people, is it the mate-chooser female who goes to such trouble to make the males desire her? To create a better range of options, perhaps?
Because among humans, as you suggested yourself, males usually have an investment of parental energy. It isn’t generally as lopsided as amongst the fish you mention but it is considerably more than, say, a Mustang stallion and his band of mares and foals.
Bingo on genetic fitness. It’s all about appearing young and fertile for a women. For our part we care about big muscles and an even bigger wallet, which can’t be faked with make-up.
I’m gone to say to my little brother, that he should also visit this webpage on regular basis to get updated from newest reports.