I am sick and tired of this strange old theory of food for sex, because it completely ignores female sex drive. Instead, it builds on an old Victorian concept of the sexless, helpless woman who is supported by a man and performs sexual duties without really wanting to.

Females simply do not function this way, and if they had done so four millions years ago, there would be no sex drive in women today. Only in a completely male-dominated environment, where men physically, by means of violence, restrain women from sustaining themselves, is there anything like food for sex - and it is forced by laws and skewed traditions.

The dumbness of this hypothesis stuns me.

Hmmm, why does this sound so far off? First, what does monogamy have to do with it? Would our little selective female look askance at some poor bloke who only brought her a paltry number of tubers while her true love was out finding a hefty batch? Why not reward him too, if there is no downside to getting "caught." Isn't it more likely that this new female selectivity was a community process, females et al started favoring a more consistent food source and this led to an entire community of gatherers? Mix that with the fact that in such a scenario minus monogamy the males as a group would have been want to protect only one female (she's better of with more protectors, no?) as they really can't tell who is their offspring? Really, its silly for anyone to think at this early point that they have found the key to understanding a theory that, in modern humans, apparently is not in evidence.

Good point, ason. I liked learning that "wear patterns and isotopes in the hominid teeth suggest a diet that included fruits, nuts, and other forest foods." Ardi & Co. ate a plant-based diet, uncooked of course, meaning our ancestors were basically vegetarian, raw foodists. Nice take-home message.

As a hypothesis, this is weaker than the aquatic ape theory.

Walking on two legs reduces the ability to gather food if searching requires a lot of time and exposure to predators because it slows you down.

With all due respect of all the great work done in the name of pure science, please do not draw a chimp standing up and call it our relative. Please,keep theoretical and application science separate from "assumed" truthful articles.

Remember the 7 steps...

Thanks.

There are plenty of monogamous animals that walk on two legs for other reasons besides sex. Ducks, and Ostriches for example. I can imagine much more simple mechanisms at play here.

Look at Meerkats for example. Taking turns standing on hind legs to scan for predators.If Ardi did this, and lived in a wooded environment, this would leave her in upright tree scampering mode.

Also grazing under low hanging branches might be a cause.

My point is that there are plenty of examples of this type of behavior and selection observable today. I am not aware of any observable instances of sexual behavior effecting locomotion today. (There probably are and I would be fascinated to learn about them)

I am inclined to think that sexual behavior followed physiological changes. It seems more logical to me. Complexity usually requires a simple foundation to build on. I am also inclined to think that the efficiency of nature is using the same processes today that it did then so we just have to look around and keep it simple.

P.S.
I now think it would be interesting to do a study of biological success rates in modern living mammals in a similar stage of development to Ardi. See weather not getting killed, or monogamy is more successful. It would be worth it just to have the argument over which mammals fit the bill.

As a female, my experience was that my sexual drive was greatest when I was ovulating...Monogamy doesn't have anything to do with it, nor does walking. Why is it so hard to acknowledge that sex has its own powerful force field; and is done, has been done, and will be done in myriad ways. One does not walk for sex, any more than one flies for sex...sex just is. I am offended by the attempt to fit it into some socio/cultural/religious gobbledegook.

Interesting also that human females tend to synchronize their menstrual cycles when in close habitation, so it's feast or famine for the males (whether evident or not). There are many unique aspects of human sexuality that invite speculation, but what do we really know?

Science has already found that women are more adapt at complex social skills, plus, with offspring to feed, care for and protect, wanting to keep a larger more powerful male around to assist in protecting them as well would make sense.

the earth and everything was created by god! he even created evolution he made and makes it happen

I found very interesting and correlated with current behavior of human males, it was not the male who spoiled the female with food, but was the female strategy to grant her favors only to the smartest gatherer available on the ancient gang, so males were forced to find different ways rather than fighting each other, and start exploring the wood, and far beyond to find more precious foods, and strange presents from the savanna or simply the neighborhood. You can observe this behavior in many birds too, and today in human males. Monogamy it is just a favorable contract for both females and males, because it protects females from violence from other males, and for males, - in favor of our own evolution path - it saves us time, because we spent less gathering food for only one female and their offspring and have more time to think about more stunning presents and more adventurous walks around, something that pushed our bipedism and our bigger brains - we may be forced to leave Africa because of food, as we will be forced in the future to leave the earth for the same reasons- . In the case of the females, they also find more spare time, because her role was a food selector, and I think that many times this adventurous male, was forced to catch a better meal before sitting down and get a scratch from her mate - like some birds do - . This also forced evolution in females brains. All in all, this sexual behavior of a very chimp like creature contribute with the path later homo-creatures took. You can see today trails of this basic behavior, males fighting each other in others fields rather than punching, and trying to find better jobs, have better careers, more resources to get acquainted with the better woman available. Polygamy is always a choice, but it has proved now and for Ardi's world, that is very demanding for males physicaly and intellectually, and stressing and risking for females. I am totally in favor of Mr. Lovejoy theory.

It makes sense that if one can walk on two legs one can use the other limbs ( arms ) to carry food. These dull toothed males may have provided more security to the females. (Hugh Heff is dull toothed and he provides well for his ladies.) The alpha males did not provide security to females. Equipped with their bristles (faster ejacc)its sounds like they were out to hit it n split it. (not share a mansion)

I don't feel this article neglects the fact that females have a sex drive. I feel that this article says that alpha males have more of a sex drive and do not care about woooing a female with food or securtiy becuase they have the power to take the female. Beginning to walk on two legs only enabled less powerful males to provide security for females.

Tom, not everyone in the world believes as you do. Please show me facts instead of spouting an opinion.

The whole reason why they bring sex into the explanation of this inefficient stance is that features evolve and persist if they improve reproductive success or survival. In this case, the halfway bipedal stance of the males allowed them to have higher reproductive success than the more ape-like males because they were able to mate with more females when they provided food. Females also gained from this adaptation because they acquired resources without spending the energy to search for them, thus improving their own survival and also reproduction (better nutrition, more fertile).
It's possible that the inbetween stance allowed them higher survival, but this is just a theory, which conveniently describes a feature of modern humans. It's also possible that the reproductive benefits of this stance outweighed the costs to survival through slower movement or higher visibility to predators.

Oh Owen Lovejoy! That food for sex theory is only slightly less dubious than the aquatic ape theory - and yet it is repeated in Science 30 years after its inception b/c the man has somehow not managed to feud with Tim White. It's based on what - reduced canine size? Well look at bonobos - they have reduced canines and they are very much the opposite of monogamous. They are equally closely related to humans, but chimps are commonly used as a model for the last common ancestor due to historical accident: bonobos were off-limits to research in the wild because they reside in war-torn regions. Furthermore, it's not even clear there was a canine reduction in Ardi - the trait is seen in many Miocene apes, so it could have been inherited, not new. Ardi strongly supports the postural feeding hypothesis. Maybe you could blog about that theory too! Looking forward to more paleoanthro coverage on your blog. . . . .

Based on my experience with the human race, I don't think it's a stretch to consider sex to be a form of currency.

Gee Tom (10/01 @10AM),
I have never heard your point of view before.["the earth and everything was created by God!he even created evolution"]
Most belivers of organized religion,usualy stick with creationism.And science or enlightned people usualy go with evolution.But this new theory is even more confusing than,biblical creation.Are you saying that Adam and Eve had(have),competition for dominant intelligent hominoid on the planet?I would love to hear you explain this,because both theories together are more confusing,than either theory on it's own.How do I know if I'm from the created side of mankind or from the evolved side?How can I tell if I was created in God's image,or if I'm evolved from a primate?Is being from one side or the other better or worse,as if a created human being is brtter than one who evolved.Please explain this,you are making my head hurt.

What the hell? What is with all the crap comments on this page? We evolved from apes. There. Done. It's a simple fact of life; so get over it! People should just learn to accept that. Females could have been won over by food, you don't know that they didn't; But doesn't mean people can go around being ignorant saying, "There's no way they did that and that's for real, just because they were apes doesn't mean they got won over by food. Everyone knows it's all about fighting with the other males." Well, here's some news for you! We DID evolve from Apes and life could have been different back then. So instead of sitting around and being ignorant, thinking you know-it-all, go out and enjoy life - it sure is more entertaining than back then...

Everyone has their own opinion. And my opinion is that this "food-for-sex" theory is highly unlikely.

It seems to me that this theory depends on the female being in a position to choose her mate....but really, how often does that happen among mammals? The strongest male doesn't get the girls because they choose him, but because he takes them. I would think that, just as a reproductive strategy, rape must be fairly effective.
On another note, I don't think this is the forum for discussions about religion, but it concerns me to see the kind of negative knee jerk reaction a mention of faith based opinion gets. We are all of us entitled to our own opinions. Yep. Every one.

Economists recently introduced the concept of money into an ape "society" to observe the effects. What was the first thing they started using it for? Sex! (http://tinurl.mobi/fghviqc
I know a lot of you won't like this, but I'm going to say it anyways. Men take women out to dinner or a movie to woo them in present day. I've lived in this world long enough to know that it often works. It doesn't mean that women don't enjoy sex, they just like a different kind of build-up to it. Similarly for the early hominids perhaps, according to Dr. Lovejoy.
Also, I believe him when he says women don't know when they're ovulating with the assumption that there was no such thing as a calendar for early hominids. Of course it's easy for us to say that women are more randy during that time, but that's only because you can confirm this by looking at a calendar and you already know that it shoudl happen once every 4 weeks. Without that knowledge (and with a tiny brain), there's no way you could figure that one out. I think Dr. Lovejoy's theory is more plausible than we care to admit.

Did Early Humans Start Walking for Sex? That was the question I believe.

I don't think any hominids within our evolutionary lineage ever walked during sex. I think all species pretty much laid down on the ground, or stood still up a against a tree or something while having sex.

Just my thoughts.

This is just cooked up theory by people who have nothing else to do, please don't waste time on such nonsense, try and solves today's problems and be of use to humanity to progress forward.

Females DO have a sex drive, but it is very true that they are turned on by things like... males giving them resources (protection, food, potential baby care, etc...). You know why? Because males owe them resources. Females are the ones who have to donate an egg and nine months of life after having sex once. So sure, they want sex, but only if they can get a male with good genes, and a good character.

What I dislike about this article is the whole "females knowing if they were fertile". (So female chimps, for example, get big red butts when they're ovulating. And that drives the males crazy; they find it very sexy.) They didn't explain it well, or offer any explanation for it.
Revealed ovulation affects both the males and females. If a male knows when a female is ovulating, he can 1) court/mate with ovulating females, 2) leave her when she stops, 3) be especially protective of her when she is ovulating. Males presumably started out only being attracted to clearly ovulating females, but basically ignoring them during other times. So for a female, it might have been very nice to conceal her ovulation - though males would like the opposite.

So, how could females have made the evolutionary jump from having revealed to concealed ovulation? That would have needed many many mutations; each step in the process would have had to have been advantageous for the individual female. Fitness, people. (:

If most females showed signs of ovulation, while a small fraction didn't, or showed less pronounced signs (due to some mutation), males would be more attracted to the females who showed signs of ovulation, ignoring the others. Their genes would say: they ones who look like they are ovulating are the ones who I should have sex with. Ignore the others. So how was this female trait adaptable?

Perhaps (near) monogamy developed first. Males supported and cared for a female whether or not she was ovulating. But during ovulation, the male would both want sex and be very, very protective (and perhaps violent). In this situation, perhaps it was individually advantageous for females to have concealed ovulation. In this way, concealed ovulation could have been selected for.

Monogamy may have been the jump start to concealed ovulation.

very interesting piece!

Meade, I think you have a very American view of what people believe. Most of the people in Europe who have any kind of religious belief, believe in a form of evolution. This does not involve Adam and Eve as they do not take that story literally, but symbolically as Jewish people have always done. The whole Creationism/Evolution debate really isn't much of an issue here, despite attempts during the Darwin Centenary year to make it one.

re:the Food for Sex theory.
There's a reason it's called "The Oldest Profession".

Well well...huH,I'v told sum of my friends that i thought of Evolution as Those wild angels who where cast-out from heaven together with the devil they soon came to earth where they mate with humans beings,so sum of them possible went into the wilderness where they MATE WITH them mankeys or champaze to form HOMOSAPIENS which then in my THEORY they soon went extinct after millions of years.So humans are derived from they own ancestors, those ancestors who did not mate with the wild angels casted from HEAVEN.

if the females arent gathering food any more why would they need to stand on two legs?

Okay I think we need to take a step back here all the people who are saying this is sexist and an ancient way of thinking... are just being way to reactive to what Lovejoy has said. And hello? This is an ancient thing were talking about here. Where males and females acted very primal and with more instinct then thought. So stop taking offense to his theory and take this into context.

The theory makes complete sense, yes there could be various other reasons and components for why we walk on two legs but this is just one guys theory.

There has always been this hunter gatherer response in every animal weather if be the female or the male. Evolution just took a curious path here, think about how the male birds collect food for the female while she tends to the babies it makes sense. Females prominently have the maternal instinct to be able to care of a baby mostly due to the fact that they carry the child. And males have the hunter gatherer instinct. His theory is connected to sex and mating rituals because at that time those were the prominent ways their society functioned. And another reason, males would fight enough other for females, we all naturally have a self preserving instinct in us. So if one smart Ardi figured out a way to not get the poop kicked out of him and mate why wouldn't their society want to follow? And if this didn't occur think of where we might be today? Women... would probably still be repressed all over the world. It takes 20 years for a society to adapt to a new way of thinking NOW let alone millions of years ago. The further you go back the longer it takes. But thats just one 18 year old's theory on a theory... which I think some people need to read the definition of theory.

I was asked to explain a better version of the above theory as a homework assignment but have since thought of none. Some of the holes in the theory listed in the comment section seem valid but most of the comments opposing the theory simply pout and scream that the theory is sexist. Does anyone have an alternative theory 1.) on why the hand and bipedalism developed in light of the factual evidence in the article and 2.) why would males bring food back if not incentivized or 3.) What other incentive could exist besides sex?

This is a great article.

I can't believe how stupid a lot of these comments are!