Dictionnaire Biologie

Dictionnaire Biologie

Menu
  • Home
  • About
  • Contact Us
  • Log in
  • Privacy
  • Latest News

Category: Updates

Sexual reproduction may not be the best evolutionary strategy. So why do we do it?

No Comments
| Updates

Most of the single-celled organisms in the world, like bacteria, reproduce asexually by making copies of themselves. So how did sex come to rule the animal kingdom? Scientists have been trying to figure out the origin of sex for hundreds of years, without much luck.

Asexual reproduction is more convenient and requires less effort: there’s no search for a partner and you get to pass all your genes along, from the U.K.’s National History Museum:

In many ways asexual reproduction is the better evolutionary strategy: only one parent is needed and all of their genes are passed on to the next generation.  All bacteria, most plants and even some animals reproduce asexually at least some of the time.
Sex is less efficient. Finding a mate can take time and energy, and any gametes that aren’t fertilised go to waste. Plus, each parent only passes half of its genes to the offspring.

But 99 percent of multicelled animals use sex to reproduce. They form gametes, mix those together and create progeny with an entirely new genome.  Scientists have long wondered what processes caused sex to evolve and become so incredibly prevalent in the animal world.

Most hypotheses about the evolution of sex point out that when genes are mixed between individuals sexually, bad genetic mutations can be eliminated more quickly than in asexual reproduction. But, since the 1880s, scientists have been unable to prove one hypothesis or another explains Megan Scudellari in Scientist magazine:

In 1886, German evolutionary biologist August Weismann proposed that sexual reproduction reshuffles genes to create “individual differences” upon which natural selection acts. Additional ideas have emerged since Weismann’s hypothesis: sex rids the genome of deleterious mutations; sex rapidly introduces beneficial mutations; sex helps organisms dodge parasitic infections. Yet these evolutionary justifications for sex have remained hypotheses because there is not enough evidence to suggest that any of them provide enough of a benefit to surmount the exquisitely high costs of sex, which include the time and energy it takes to find a mate, the passage of only half of one’s genes to the next generation, and the breaking apart of favorable gene combinations.

Part of the problem, Sculdellari says, is where scientists look to try to test these ideas. Most of the organisms we know the most about sexually like flies, humans and bacteria only reproduce sexually or asexually. But there are some species that can do both depending on the environmental circumstances surrounding them. Yeast, snails and rotifers, microscopic freshwater animals reproduce both sexually and asexually. By studying these organisms, scientists can compare the relative health of their asexually and sexually produced offspring.

The Red Queen hypothesis, named after the Alice in Wonderland character, suggests that sex is really about eliminating the chance of disease through the exchange of cell surface genes that alter the proteins where diseases try to invade:

The Red Queen hypothesis for sex is simple: Sex is needed to fight disease. Diseases specialize in breaking into cells, either to eat them, as fungi and bacteria do, or, like viruses, to subvert their genetic machinery for the purpose of making new viruses. To do that they use protein molecules that bind to other molecules on cell surfaces. The arms races between parasites and their hosts are all about these binding proteins. Parasites invent new keys; hosts change the locks. For if one lock is common in one generation, the key that fits it will spread like wildfire. So you can be sure that it is the very lock not to have a few generations later.

Evidence in a species of New Zealand lake snail shows that those that produced sexually were much less likely to be infected by a common parasite than those that were the product of asexual production. But in subsequent generations that pattern flips, which may mean that for organisms that go both ways, reproductively, the ability to switch itself conveys a benefit.

Looking for evidence explaining why sex persevered is even more complicated. We may someday know why sex started in the first place, but figuring out why asexual reproduction was never resurrected in the animal kingdom is trickier.

Sex allows species to adapt to the loss of food sources, the arrival of parasites, rising temperatures, and more. There is some doubt, however, whether the environment fluctuates fast enough to warrant the prevalence and persistence of sex in the eukaryotic kingdom. “Is the force favoring sex large enough in the face of the costs?” asks theoretical biologist Sally Otto. “The niggling doubt in the back of my head is that it is not.”

Read More »

Is Sex For Pleasure Uniquely Human?

No Comments
| Updates

We are apes. We are animals. We are made of the same organic molecules as all life. We metabolize. We procreate. We die. But we are also human beings. We have language and culture. We self-reflect and ponder the future. We have medicine. We use advanced tools, like televisions, smart phones, and computers.

We also have sex.

We have a lot of sex. In human culture, sex is so much more than a means of reproduction. Sex is emotional. Sex is communicative. Sex is fun. And when it comes down to it, for most of us, sex just feels good. We have sex for pleasure significantly more often than we have sex for reproductive purposes. Is this one of those things that makes us uniquely human?

Well, here’s where things get complicated. How do we know what feels good to an animal? It’s not like they can tell us. Perhaps all animals have sex for pleasure. Perhaps we are all hard-wired to experience pleasurable feelings during the act of sex for the very purpose of procreation. I sincerely doubt that most animals are aware of the fact that sex leads to offspring. They probably do it because it feels good. Science has done a pretty good job of exploring and explaining precisely how sex feels so good to us. But answering the question of why it feels so good is seems to be a matter of conjecture. Granted, if it didn’t feel good, we might not do it. And if we didn’t do it, there wouldn’t be any of us here to have this discussion.

One indication that animals enjoy sexual activity is the act of masturbation. We’ve all seen our dogs do it. Male dogs will pretty much hump anything they can wrap their legs around. Masturbation in horses is also quite common. There’s even a seminal (no pun intended) paper on squirrel masturbation. In fact, a lot of animals go solo. Birds, walruses, sheep, turtles, elephants, bears, and many more species have been observed engaging in autoeroticism. Porcupines have even been witnessed to fashion vibrators out of sticks. Interestingly, although all of these animals have been documented to play with themselves, it is exceedingly rare that they actually get off. That is, masturbation to the point of orgasm/ejaculation appears to be a fluke outside of the human species (except maybe in squirrels).

What makes us so different that our masturbatory experiences are “goal-oriented” when other animals’ are not? And why is our masturbation frequency significantly higher than that of other species? Jesse Bering hypothesizes that it is because humans have the unique ability to form mental representations of erotic material. It may be the case that what sets us apart is our ability to write, produce, edit, and even star in our own mental porn.

I know that masturbation may not be considered sex, per se. You’ve probably heard the rumors that dolphins are the only other mammals that have sexual intercourse for pleasure. It appears as though this is almost true, depending again on how one defines sex for pleasure. Dolphins have been observed to have sex during all stages of the female menstrual cycle, not just ovulation. But, as they have been apt to do lately, our favorite ape relatives, the bonobos, have to be included in this conversation. Bonobos get it on year round as well. As far as I know, no other animal species has been documented to engage in full-on intercourse even when females aren’t in heat. So in a way, when our thoughts and behaviors are dominated by non-stop, year-round sexual urges, we aren’t really acting on animalistic impulses. We are doing something that is almost uniquely human. If we were to actually “do it like they do on the Discovery channel,” we’d only be getting it on a few days each month. So the next time I hear somebody quote the Nine Inch Nails song Closer, I’ll remember that I’d rather do it like a human, thank you very much.

Read More »

Yes, Other Animals Do Have Sex For Fun

No Comments
| Updates

There’s an idea circulating that humans are the only animal to experience sexual pleasure; that we approach sex in a way that is distinct from others. As with many questions about sex, this exposes some interesting facts about the way we discuss the subject.

On one level, the question of whether humans and nonhumans experience sex in the same way is fairly simply dismissed: how would we know? We cannot know how a nonhuman experiences anything – they can’t be asked. Sex as an experiential phenomenon for nonhumans is, quite simply, inaccessible. Science is obliged to propose questions that are answerable, and “how does a leopard slug experience sex?” is, at time of writing, about as unanswerable as they get.

Having said that, we can make educated guesses about whether sex is pleasurable for other species. Sex would be a very strange thing to seek if it didn’t bring some form of pleasure. It increases risk of disease, it wastes energy, it can seriously increase the likelihood of something bigger coming along and eating you.

There’s no reason why an animal should seek sex unless they enjoy it. It is often proposed that an inherent “drive to reproduce” explains nonhuman sexual activity, but that is not an alternative here: if animals possess an instinct to reproduce, it needs to function somehow – and pleasure is a fairly basic motivator. The hypothesis that all sexually reproducing species experience sexual pleasure is, in itself, quite reasonable – as would be the hypothesis that animals find eating pleasurable.

Do Monkeys Have Orgasms?

This hypothesis about sex has been tested. Since the word “pleasure” is quite vague, scientists have tended to focus on orgasms. As a particularly intense form of sexual pleasure for many people, the logic has been that if non-humans experience orgasm, they are almost certainly experiencing pleasure.

Given that we are most familiar with human orgasms, scientists have unsurprisingly looked for behavioral and physical correlates of what we sometimes experience – shuddering, muscular rigidity, a cessation of movement, vocalization, changes of facial expression, ejaculation. None of these are guaranteed, and consequently we should not expect them necessarily to be associated with sex in other species. But using this method, most commonly to study non-human primates, the animals perhaps most likely to display responses similar to humans, scientists have detected orgasm in many different species including macaques, orangutans, gorillas and chimpanzees.

In fact, very few primatologists doubt that non-human primates experience orgasm – at least, male non-human primates. There is debate as to whether female primates (including humans) experience sexual pleasure in the same way male primates do, which raises some fairly important questions about how Western culture views female sexual agency. But some detailed studies of the stump-tailed macaque have suggested that females of this species, at least, demonstrate a capacity for orgasm.

Defining Pleasure

Drilling down the totality of the “experience of sexual pleasure” to the moment of orgasm is problematic, though. It is the result of the pioneering work of Masters and Johnson dating from 1966. They focused sexual pleasure on orgasm by proposing a four-stage biomedical framework of excitement, plateau, orgasm and resolution. Despite much criticism, it entered intellectual and public consciousnesses as a description of “normal” sex, involving genitals and aimed at producing orgasms.

But while this may describe sex for many, it excludes an awful lot of people. A brief survey of the various things that humans get up to quickly indicates that sex isn’t necessarily focused on orgasm or genitals. Focusing sex on genitals and orgasm only makes sense if we assume that the central function of sex is reproduction – exactly the same assumption that seems to lie behind scientific inquiries into sexual pleasure in other species.

Various cultures maintain that sex is not connected to conception, though – most famously the Trobriand Islanders of the South Pacific. New reproductive technologies have meanwhile separated sex and reproduction: it is not necessary for a people to have sex in order to conceive. This shouldn’t come as much of a surprise, given that people have more sex than they have children. The yoking of sex to reproduction to the exclusion of pleasure can be traced to the Victorian era, and is the consequence of all sorts of exciting historico-political processes that would take a whole separate article to explain, but it seeped into all aspects of Western culture, including science.

Not Just for Reproduction

Not to suggest that sex isn’t involved in reproduction. The gamete exchange that is necessary for conception to occur is, in general, the result of some form of contact between bodies. But when people say that “humans are the only species to have sex for pleasure” they are really saying that “humans are the only species that has non-reproductive sex.”

In fact, sex may well serve a number of other functions. Sex may bond animals together or may cement a dominance hierarchy in the case of bonobos, for example, one of humans’ closest relatives. These functions may be extremely important, especially for social animals, and would likely only be feasible if sex were in itself a source of pleasure.

There is also no shortage of examples where non-human sex has nothing to do with reproduction at all. Females of many species mate with males when they are non-fertile (marmosets for example). And same-sex sexual behavior, which is definitionally non-reproductive, occurs in every vertebrate species in which it has been looked for, along with some non-vertebrates (bedbugs, for example, or fruit flies).

This evidence alone should lead us to expect that many animals experience sexual pleasure in much the same way that humans do – that the pleasure involved in sex leads many animals to seek it in non-reproductive contexts, and that this aspect of sexuality is not as unique as humans may like to think. This insight is surely vital to understanding sex in other species, not to mention all other aspects of their behavior too.

Read More »

Meet Eight Species That Are Bending the Rules of Reproduction

No Comments
| Updates

When it comes to getting creative in the bedroom, we humans may think we’re the experts. In fact, we’ve barely scratched the surface of how varied and multifaceted reproduction can be—just look at species that do the deed through kinky-sounding strategies like sperm sequestration, “virgin births” via cloning or even hybridizing with other species. These may sound like show plots of a new series on the Space Channel, but they’re actually just some of the many tricks that Mother Nature uses to stay a few steps ahead of Cosmopolitan Magazine’s sex tips.

Moreover, some of these unconventional methods are making scientists rethink the basic tenets of reproductive biology, says Ingo Schlupp, a professor of biology at the University of Oklahoma. His study subject, the asexual Amazon molly fish, defies the so-called rules of reproduction by making perfect clones of itself, sans males. With such a lack of genetic diversity, these finger-sized fish should have been wiped out by disease long ago, Schlupp points out.

“How on earth do these guys survive for such a long time without any recombination?” he says. “To me that’s a real head scratcher. Here’s a species that doesn’t [recombine their genes every generation] and theoretically should have been dead many thousands of generations ago, but yet they’re living happily.”

We still haven’t unraveled all the mysteries. But one thing’s for certain: The more we learn about “alternative “reproduction strategies across species, the more we realize that many of them might not be so alternative after all. Now that they know what to look for, biologists are finding more and more cases of strange and hitherto unknown forms of animal procreation. In other words, baby-making outside the “traditional” male-female pairing could be far more widespread than we humans are inclined to think.

Roughly 100,000 years ago, in a romantic lagoon near Tampico on Gulf side of Mexico, two distinct fish species—a sailfin molly male and an Atlantic molly female—came together in an unlikely union. The colorful pair gave birth to the Amazon molly: an all-female, asexually reproducing mini-carrot length fish named after the all-female tribes of Greek legend, according to Schlupp of the University of Oklahoma.

Yet while these Amazons need no male genetic material to reproduce, they’re not entirely independent. To kickstart their reproductive systems, they still need sperm. In a bid to find a suitor into this kind of thing, Amazons will actually disrupt mating processes between sexually reproducing mollies they come across in an effort to steal the male’s seed from his erstwhile mate—by literally squeezing in between the pair.

“They kind of butt in and then it’s almost as if they’re hoping to get the mating that was meant for another female,” Schlupp says. “The males that these Amazon mollies are mating with really have to get up close and personal with the Amazon mollies. These fishes have a specialized fin that they use to transfer sperm—we’re actually talking about real copulation. It’s not like a mass spawning where some parasitic female swoops in and gathers some sperm.”

Read More »

What the heck are Squishies?

No Comments
| Updates

You must have seen the famous squishies by now. They are everywhere. In stores, on Instagram, at your friends’ house – they’ve become omnipresent.

But, you may be wondering what precisely they are. Worry not, you’re not alone. Simply put, they are squishies. You may think this doesn’t explain anything, but it does. You squish them, hence the name.

What are squishies?

These soft toys are made from polyurethane foam. When you first take them in your hand, they’ll have a similar feel to a stress ball. But, they are so much more. Like a stress ball, you can squeeze them as much as you like and they’ll always revert to their original form. However, unlike the stress ball, they come in many fun shapes and sizes.

You can get animal squishies, food squishies or a squishy that looks like your favorite cartoon character. The possibilities are endless! And, we mean that. You can even get a combination squishy, like a mix between your favorite food and animal. It might sound weird, but it’s adorable, believe us!

Looks so pretty and smells even better

If the fun size and the bright colors aren’t enough for you, you can get a scented squishy, as well. Most of the scents are food-related, so your banana squishy can smell like a banana, too. Imagine squeezing your cookie squishy and smelling that freshly-baked scent all day. Sounds nice, right?

Size is everything

Just because they’re usually small, it doesn’t mean you have to limit yourself to a tiny squishy. You can also get jumbo-sized squishies for your bed or desk. Or, you can go even smaller and get a tiny one for your keychain.

Who thought of this?

The Japanese, of course. These squishies are the epitome of Kawaii, a word that means “cute”or “adorable” in Japanese. In fact, squishies were born in the capital of cuteness – the Harajuku district of Tokyo. They were created over thirty years ago as a toy appealing to all ages. They have been a beloved pastime in Japan ever since. However, their popularity outside of Japan started skyrocketing just recently.

The first squishies were in the form of famous Japanese characters, like Hello Kitty and  Rilakkuma. However, soon the trend started to spread like wildfire, and squishies soon took the shape of favorite snacks, beverages, animals, etc.

The soft design and delicate texture made them instantly popular among both young and adult kawaii culture lovers. They come in all sizes, so they can be used as accessories for bags and briefcases, phones, keychains and so much more.

Why are they such a trend?

Squishies are perfect accessories, bringing that much-needed touch of cuteness to your outfit. They also help people express their interests and hobbies. Furthermore, they are great collectibles.

Squishies are a real dream for collectors of cute pop culture paraphernalia. You can collect them and swap them with friends, or show off your collection to other enthusiasts.

However, that’s not all. Squishies are also great stress relievers. They function like a stress ball. You can use them to get rid of excess energy and focus on one task while your stress levels go down. They’ll never lose shape, no matter how many times you squeeze them. They are soft and have a pleasant texture, so you’ll enjoy playing with them.

A soft, brightly-colored stress relief? What more could you ask for, really? Carry them in your bag, on your keychain or phone for instant access to the most adorable stress relief ever.

 

 

 

 

 

 

 

Read More »

Twitter

Tweets by FatheringIntent

Recent Posts

  • Sexual reproduction may not be the best evolutionary strategy. So why do we do it?
  • Is Sex For Pleasure Uniquely Human?
  • Yes, Other Animals Do Have Sex For Fun
  • Meet Eight Species That Are Bending the Rules of Reproduction
  • What the heck are Squishies?

Recent Comments

    Categories

    • Updates

    Follow Me

    • tumblr
    • pinterest

    AFFILIATES

    Dictionnaire Biologie 2021 . Powered by WordPress