Matt Abramson

11/19/08

Professor Dolby

Human Animal

Mate Choice

In both humans and animals alike, the process of sexual selection and mate choice is crucial to the survival of the offspring. Sexual selection is based off of the Darwinian theory of survival of the fittest. Mate selection is designed to help individuals attract the fittest partner possible and maximize the chance of getting chosen themselves. In both humans and animals, the best genes and most attractive mates are the ones most sought out for. Sexual selection is one form of natural selection that is focused on the competition for mates. Nobody, no matter what species, male or female, wants to find them self alone and without a mate or offspring. Finding the right mate is a very significant process for both humans and animals because it is the single way to ensure that your genes get passed on to the next generation. Through evolution, adaptation, and sexual selection mate choice continues to be the most important factor in natural selection because it encourages natural selection, passes on the most beneficial traits to a particular species, and produces strong offspring for future generations.

Sexual selection results in competition in all species to fight for the mate with the best genes. In most species the male is the one who has to fight to win the mating rights to the female. Females may be more selective in the mating process because they have more invested in each gamete and in the resulting offspring. “And because the availability of eggs is a limiting factor in reproductive success, males tend to compete for female attention and not vice versa (Dugathin, Godin 56).” A male is able to produce millions of sperm and can pass on his genes through many different partners. Females are not passive participants in sexual reproduction (Birkhead 66). “Females generally devote much of their adult lives to raising their young and may spend weeks or even months, therefore, selecting a reproductive partner, males, by contrast, exhibit a willingness to reproduce indiscriminately, regularly attempting to mate with practically any familiar females, any unfamiliar females, and any convenient motor vehicle left unattended for more than an hour (Douglas 34).” For a female, it is necessary to find a mate that is most suitable to take care of the offspring and pass on the best genes.

A female’s choice for a particular mate is not as easy as it may seem. In most cases a group of males are not conveniently lined up for her to make her pick, as is the case with sage grouse. For this early spring bird, males congregate in mating areas which are referred to as leks (Dugathin Godin 56). At these leks males do what they can to impress a female to convince her that they are the right mate with the best genes for her and her offspring. In most instances a female must compare males in individual meetings. First a female must search for a suitable male, which can be difficult when her search could be limited by the number of predators or how spread out a population is. Once, she finds a male she must then make the decision on whether to reject him or accept him as a mate. Human young have an extremely long period of dependency and require years of care and attention if they are going to survive, which is easiest to achieve when both parents share the work and responsibility (Douglas 35). In most human societies it is the women who take on the majority of the child rearing responsibilities, while the men still contribute. During Homo Sapiens’s earlier, less civilized era, a male looking for a partner would do what he could to exhibit size, strength, and access to baby-rearing resources like food and territory, all of which would give offspring he sired a greater chance of surviving (Douglas 36). These traits and beneficial resources greatly increase the male’s chances of being chosen as a mate.

Recent evidence has indicated that females prefer mates with traits that stimulate their senses. In some cases, females may favor mating with a male that is loud or brightly colored simply because he is easy to locate. Reducing the amount of time it takes to find a mate may reduce a female’s risk of being killed by a predator (Dugathin Godin 57). Certain species of birds, frogs, and other reptiles use their fascinating colors as a means of attraction (Miller 390). Peacocks are one animal that exemplify this finding. Male peacocks have elaborate tales that they flaunt proudly whenever they are interested in pursuing a female. As pleasing to the eye as these Wedekind is testing women’s responses to sweaty T-shirts–men’s sweaty T-shirts. He has found that women have strong preferences in that department. They’re attracted to the scent of men who are most unlike them in a very particular way–in the array of immune system genes known as MHC, for major histocompatibility complex.biological traits are, they do not offer any beneficial traits to a female or her offspring. A study on guppies showed that the most colorful male was indeed the most attractive for females. However, the offspring that inherited the vibrant colors were actually less likely to survive (Sapolsky 18). For many birds and mammals, natural selection appears to favor females who choose mates that provide them with some direct benefit that will increase their fecundity, their survival or the survival of their offspring. Such benefits might include food, a safe haven, or even the prospect of fewer parasites (Dugathin Godin 59). When males provide no obvious resources, such as food or protection, females may choose to mate with the males that appear to have the best genes.

As part of mate selection, males must compete for the rights to a female. Sometimes when there are two or more males competing for a female the competition can turn violent. In many animal species males will fight to the death in order to secure their place in sexual reproduction. Such male-male Such male-male competition leads to intrasexual selection among males–evolutionary selection for traits that increase a male’s ability to compete with other males for reproductive access to females.competition leads to intrasexual selection among males- evolutionary selection for traits that increase a male’s ability to compete with other males for reproductive access to females. However, females can still pick and choose out of these contests and as a result intersexual selection for male traits that can influence female mate choice occurs (Ben-Ari 7). Sexual trails–head length and width, antenna length, fore-tibia length–are traits that play a direct role in the male-male encounters that determine which individuals have access to females (Lundmark 304). Such sexually selective traits raise the question, do these masculine traits continue only because they grab the attention of the female, or does it demonstrate some aspect of a male’s fitness (Lundmark 304)? In today’s society humans possess great physical fitness, which is demonstrated in sports and other physically demanding activities that appeal to females. Physical fitness is an important trait that no female would refuse to pass on to her offspring.

Not all competition is violent however, as is displayed by schools of guppies. When a predatory fish approaches a school of guppies, males, usually in pairs, cautiously approach the potential threat to “inspect” it. Risky behavior, such as this, has been observed in many species, and behavioral ecologists have suggested that bold males may swim close to a predator to advertise their vigor to nearby females. Laboratory studies have shown that when no females are present, however, no male guppy plays the hero by approaching the predator more often than his counterpart (Dugathin Godin 61).

Not all attraction is based solely off of who has the best genes for sexual reproduction. As humans well know, attraction can be based off of looks. Although males have always had the reputation of being “shallow” individuals, basing their mating decision off of physical qualities, women too have specific preferences. Some physical features which women generally prefer a male partner to have are a square jaw, an angled chin, and a high forehead. Evolutionary psychologists have found evidence that ovulation heightens women’s response to the pheromone androstenol–a contributor to male body odor–and to the sight of strong male facial features, ones that emphasize secondary sex characteristics. But the increased appeal of attributes conveying a sense of strength, aggression or dominance is only one part of the finely tuned mate-identification system (Diller 120).” Women prefer more masculine faces during ovulation and more feminine features during other points of the menstrual cycle. Men’s notionsWomen prefer more masculine faces during ovulation and more feminine faces at other points of the menstrual cycle. Men’s notions of attractiveness (such as ideal hip-to-waist ratio), on the other hand, remain relatively constant over time.Women prefer more masculine faces during ovulation and more feminine faces at other points of the menstrual cycle. Men’s notions of attractiveness (such as ideal hip-to-waist ratio), on the other hand, remain relatively constant over time. of attractiveness (such as ideal hip to waist ratio), on the other hand, remain relatively constant over time (Diller 120). Features that men find attractive include facial symmetry, youthful skin, and a waist-to-hip ratio of 0.7 (Lundmark 304).

Another feature of attraction for females is their sense of smell. Claus Wedekind, a zoologist at Bern University in Switzerland. Zoologist Claus Wedekind of Bern University in Switzerland conducted a lab in which he tested women’s responses to sweaty t-shirts worn by different men. It was shown that women are attracted to the scent of men who are most unlike them in a very particular way-in the way of immune system genes known as MHC, for major histocompatibility complex. Attraction based off of the sense of smell is not limited to the human species but can also been seen in animals. In a 1974 laboratory test conducted by biologist Lewis Thomas, mice were able to detect the different odors of mice around them, by distinguishing the different odors given off by the MHC genes. Young mice tend to prefer the odor of their nest mates, but when they hit puberty they prefer mice with MHC genes that are unlike their own (Richardson 26). Since humans and animals are attracted to HMC odors that differ from their own, scientists have developed a theory that there must be some advantage to choosing a partner with dissimilar HMC genes (Coghlan 12). One possibility is that the attraction of dissimilar HMC genes reduces the risk of inbreeding. Another theory is that children will have a better chance fighting off parasites and diseases if they have a mixture of HMC genes (Coghlan 12). Whatever the reason, it seems that differing HMC genes are a factor to subconscious attraction.

Mate choice is a factor of human nature that is prevalent in both humans and animals. Sexual selection is a method in which females differentiate which males would make the best mates for them, based on beneficial traits and genes. Attractiveness to physical features is not shallow; it is human nature that both males and females possess. Sexual selection is not limited to physical appearance but also includes the sense of smell. When choosing a mate, a female must make her decision based on what qualities a male has that will benefit her and her offspring. When a male makes his decision for a mate, if he indeed does get to choose, he is ensuring himself that his genes will be passed on to the next generation. Mate selection is just one piece of the puzzle that encompasses the survival of all creatures and natural selection, and it is crucial to the existence of all creatures on earth.

Comments are closed.