Unless you're this guy, you probably know that kissing does not make babies. So what, you might wonder, caused kissing to evolve as part of the human sex act?
Well, researchers suspect that kissing evolved as a means to immunize women against illness prior to pregnancy--read the full article here.
-Mindy MacKay
Thursday, March 22, 2012
Tuesday, March 13, 2012
The Evolution of Sociality in Primates
Why are primates so social? Also, more specifically, why are humans so social? With the exception of primates, very few mammalian orders contain species that exhibit social behavior. Shultz et al. have provided several clues as to why primate social behavior is so different from other mammalian orders by examining data from the past 74 million years!
They discovered that the most crucial step towards sociality occurred when primates began to become diurnal rather than nocturnal. When primates were nocturnal, they tended to be solitary foragers that could avoid detection by hunting quietly in darkness. When primates began to hunt during the day, their activity became more recognizable to predators simply because they could now be detected more easily in the light. Primates who travelled and hunted in packs were more likely to survive, and thus more social primates evolved by means of natural selection. These primates were less likely to become victims of predation because each predator would only kill one or two primates in a group and, as a result, the vast majority of the organisms in the group would survive each predator attack. Also, having more primates to compete in each predator attack increases the likelihood that the predator will either die or retreat. The research suggested that these social groups were only loosely bound: members could come and go as needed. Behavior similar to this is present today in lemurs. Primates did not begin to form small groups with close social links until millions of years later.
Unlike all other primates, humans have the ability to cope in numerous different social settings. Over time, we have functioned in many complicated social settings: monogamous versus polygamous societies, nuclear family versus extended family groups, various work settings, etc. Our social flexibility both in groups and in wider society is unmatched by any other species. Shultz et al. discovered that this is a result of increased brain power (humans have more brain power than any other species). This makes perfect sense: increased brain power allows us the ability to adjust to changes in our environment. No other organism has the mental complexity to surmount this obstacle. How cool is that?
-Cristina Terhoeve
Share the Love: A closer look at polygamy
When you’re little, everything seems so simple. You grow up. You fall in love. You get married. You have a family. At least that’s what I thought life was like, but I would soon come to find out that, for better or for worse, nothing in the world is that straightforward. “Alternative” types of relationships are getting increasing media attention. TLC broadcasts Sister Wives, a reality television series featuring the polygamist Brown family, and open relationships and open marriages are not unheard of. But such does not come without criticism. In his book, Opening up: a guide to creating and sustaining open relationships, author Tristan Taormino claims some of the most common criticisms to polygamy include “the monogamous person is being taken advantage of,” and “the non-monogamous person wouldn’t be doing this if she really loved the monogamous person”. Words like “sexist”, “coercive” and “patriarchal” have even been thrown around, and many groups, including numerous churches, claim that polygamy is an “abomination”. But what makes it so detestable? Can polygamy really be considered unnatural?
No. In fact, it’s quite the opposite. Cases where polygamy has naturally evolved are widespread and incredibly diverse. A vast number of species, we know, are promiscuous, meaning any male will mate with any female. But there are also many polygamous species, where a single individual maintains relationships with multiple mates. LiveScience published a list they call the “Top 10 Swingers of the Animal Kingdom”, species that break so-called norms. As one might assume, included on the list are lions, which are largely known to live in prides in which few males have mating rights to a large number of females. But also making appearances are (among others) walruses, African blue-headed lizards and bronze-winged jacanas, a tropical species in which females maintain a harem of males to raise her many clutches of eggs. Although not polygamous like the previously listed species, bonobos also make the list for their unique approach to sex. These promiscuous primates have been known to form short-term heterosexual, homosexual and even incestuous unions, and live in relatively peaceful societies. The frequent sex in bonobo societies is thought to “strengthen social bonds and resolve conflict”. Taking a look at the animal kingdom quickly shows us that monogamy is not the only answer, and promiscuity and polygamy are far from unnatural.
Now for my two cents. Individuals cannot choose to be a certain way, just like species cannot choose to evolve in a specific direction and what works for some is not necessarily what’s best for others. So ignore what your neighbor’s doing. Every human, just like every species, is unique and has their own way of doing things. That’s what makes life so fascinating.
The full LiveScience article can be found at: http://www.livescience.com/12963-top-10-polygamous-animals-bonobos-hyena.html
-Elizabeth Richardson
Putting the Ant in Infanticide
When thinking about sociality and how it evolved, ants are some of the first examples to spring to mind. Not only does each individual share resources, there is an entire caste of sterile females who never breed at all. The existence of sterile castes in ants and other eusocial insects is curious, because a mutation which removes the ability of the workers to breed seems obviously deleterious: no breeding, no fitness. The mechanism which brought this sterility about had historically been under some debate. Opinions were split between kin selection (improving the fitness of other, genetically related individuals improves your fitness as well), or some form of parental modification in which the queen actively suppressed the development of her daughters. To settle this debate, researcher Joan M. Herbers reasoned that studying the sex ratios of a colony would provide the data to conclude one way or another.
The premise of her idea is that each evolutionary mechanism would effect the sex ratio in different ways. Supposing the queen is in total control, and suppresses her workers, the sex ratio would reflect the optimum fitness ratio for the queen’s genes: a even distribution of males and females. However, if kin selection is the mechanism behind the development of sterile worker castes, the sex ratio would be approximately three females to every one male. This is because ants, like all hymenopterans, have a haplodiploid sex determination system. Instead of combinations of X and Y chromosomes determining gender, male ants emerge from unfertilized eggs, and are haploid, while females emerge from fertilized eggs, and are diploid. Assuming the queen mates once, that means that each of her daughters will share an average of 75% of her genetic material with her sisters, but only about 25% with her brothers. Because sisters share more genes with each other than with their brothers, kin selection results in strong selection towards a 3-1 female to male sex ratio.
Armed with this knowledge, Herber started gathering sex selection data for the ant species Leptothorax longispinosus, controlling for other variables that can alter sex ratios. What she found was that queens actually do produce an even ratio of male and female children. However, the measured worker sex-ratios were always around 3-1. The answer to this puzzling contradiction? Far from being developmentally and behaviorally suppressed by the queen, workers were actively killing and eating their infant brothers, enforcing the sex ratio in their favor. Thus, Herber concluded that kin selection is the primary mechanism of eusocial evolution in the species.
The full article can be found here: http://www.jstor.org/stable/2408712?seq=2
-Adam
Well I guess that’s why they’re called fruit bats.
Homosexuality has sparked scathing debates in modern society, not only in a religious setting, but in the politics that keep our everyday lives running. The argument rages between people who would eradicate discrimination in the workplace, military, and education system, and those who believe love between two people of the same sex is an abomination. One popular argument against homosexuality is that it “goes against human nature” in that it does not lead to reproduction. However, observations by zoologists suggest that this argument is evolutionarily unsound.
Scientists have observed individuals in several species, including penguins, ostriches, and even monkeys, both in the wild and in captivity, that will display interest only in their own gender even in the presence of potential opposite-gender mates. It may be surprising to some that this behavior serves a variety of purposes in the animal kingdom, including playing a role in reproductive success.
For example, primatologist Amy Parish postulates that female macaques engage in homosexual behavior to increase their social status, thus increasing their chances of breeding. By taking control of a resource—in this case, other females—a female macaque makes herself a favorable partner in an alliance or potential mate. Other proposed motives for homosexual behavior in animals include means of resolving tension (in bonobos) and friendship bonding (in dolphins). Despite progress in the field, though, animal homosexuality remains a misunderstood subject because many scientists are afraid to ‘get in trouble’ socially and politically.
What do I think? Well, first, a disclaimer: I hold myself to no particular religious belief. I don’t know and honestly couldn’t care less about what’ll happen to me when I die. That doesn’t mean I don’t have my own set of naïve, inflexible beliefs, though. Personally, I hold love, whether homosexual or heterosexual, as something pure and sacred. It unsettles me to think of it in cold and clinical terms, as a mechanism for reproductive success rather than just ‘that warm fuzzy feeling when nothing matters and you can do anything’, even though that notion is juvenile and the reproductive success thing actually has validity. But then, just because I don’t particularly like the facts doesn’t mean I should disregard them.
In conclusion, we may never know the truth behind why people, or animals, love who they do, but for now, we have patterns, theories, and facts.
Read more about it at National Geographic:http://news.nationalgeographic.com/news/2004/07/0722_040722_gayanimal.html
-Mindy MacKay.
Prehistoric Chirping: How Crickets Have Kept Their Call
One of the difficult things about trying to determine behavior and interactions between species that have gone extinct is that, for obvious reasons, there aren’t any living members of that species to observe. However, a research group in China has managed to do the next best thing: Take the fossilized remains of a Jurassic-era katydid namedArchaboilus musicus and reconstruct the type of chirp that it would have made to communicate with others of its species. By looking at models of the stridulating wings and comparing to species alive today, the group was able to determine the frequency at which the cricket would have to stridulate in order to produce its characteristic chirp.
The most interesting this about this is that in the 165 million years since this species existed, there are still many species of cricket that maintain this same method of communication, with almost no change in the actual mechanism of stridulating. This means that the katydids of the Jurassic era were already capable of communication in this manner, and that natural selection favored this method of chirping enough so that the mechanism survives in descendant species to this day. The paper can be found at http://www.pnas.org/content/early/2012/02/02/1118372109.full.pdf+html, and they even have a short soundfile of their predicted sound of the katydid in question at http://www.pnas.org/content/suppl/2012/02/03/1118372109.DCSupplemental/sm01.mov
-Eric Baeuerle
Early Evolution of Eusocial Organisms
I’ve always thought that eusocial organisms, like termites, ants, and some bees, were rather fascinating to study, but no one really knows how eusociality developed because these advanced taxa evolved so long ago. What’s cool now, though, is that Bryan N. Danforth has started looking at halictid bees, which are primitively eusocial, and has found that studying their behavior gives some insight into the early evolution of the advance eusocial taxa. If you want to learn more about this, you should read his paper.
-Elizabeth Richardson
Singing Mice
Singing mice? That sounds like something from a fairy tale! Indeed, Disney’s portrayal of musical mice, from the singing friends of Cinderella to the whistling Steamboat Willie, seems far from accurate. Interestingly enough, however, new research shows that mice actually do have their own courtship songs using ultrasonic frequencies, which may even rival the complexity of bird song. What’s even more interesting is that females can tell the difference between the songs of brothers and those of unrelated males! You can follow the link to read the full article, it’s pretty cool. Check it out!
-Elizabeth Richardson
Current Social Networks Older than We Think
http://arstechnica.com/science/news/2012/01/studying-people-of-the-past-with-people-from-the-present.ars
New research suggests that current humans share many elements of their sociality with hunter-gatherer societies from the late Pleistocene era. By polling the Hadza, a present-day hunter-gatherer society in Tanzania, researchers found that the ways in which the Hadza relate to each other are quite similar to how people living in industrialized communities interact. The distance between the homes of individuals influences whether or not they will become friends, as do similarities in physical appearance. Perhaps most relevant is the finding that people who cooperate and share resources are more likely to be friends - the same is true for “non-cooperators”.
-Kendall Post
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