We won’t be on this earth if not for sexual reproduction. It is through this process that we inherit traits from either one of our parents. Although we get their traits, we are not identical to them. Essentially, sexual reproduction produces a variety of offspring. Humans are not the only ones who can output offspring through this method: animals and plants reproduce this way too.
Basically, through sexual reproduction, new gene combinations are introduced into the population through genetic recombination. Although we are brought into this world through this process, there are questions thrown out there regarding the need for sex. As that question is pondered on, it leads us back to the evolution of sexual reproduction.
The Evolution of Sexual Reproduction
Why have sex? That is the question. Why should we dedicate part of our lives in search for a mate? This is the case for both humans and all the other creatures in the animal world.
To reproduce sexually, males and females need to find a mate. In the animal kingdom, the female generally makes the choice and all the males need to do is compete in order to be chosen. In other words, so much effort is put into being able to reproduce. In fact, some animals fight to the death just for the right to be the chosen mate.
While “fighting to the death” to secure a mate isn’t exactly how human relationships is best described, the connotations are there. We have to compete with several other humans in every part of the world for the chance of securing a partner with whom we might be able to produce an offspring. So the point about competition still sticks. And some get lucky while others don’t.
Compare this to those who reproduce asexually. Through asexual reproduction, offspring that is exactly identical to their parents are produced. Not only that, it only takes a single parent to produce such an offspring. Also, with asexual reproduction, twice as many offspring can be reproduced.
But in order for a population of any organism to survive, they need to be compatible with their environment, and environments aren’t static – they too evolve. So in order to adapt to an ever-changing world, populations need to change their genetic makeup and that means changing their genes.
With asexual reproduction, the offspring are basically carbon copies whereas sexual reproduction involves two parents with the offspring taking traits from each. What this simply means is that the chances of survival is higher in offspring created through sexual reproduction as they are different from those that came before them.
So if asexual reproduction is an evolutionary dead end, why are there still two sides to the need for sexual reproduction? To understand this better, here’s a look at the advantages and disadvantages:
List of Advantages of Sexual Reproduction
1. It helps natural selection remove harmful mutations from the population
In a study called Sex: Why Bother? Research on Pros, Cons of Sexual Reproduction Explained which was highlighted in Science Daily in 2006, researchers examined one of the benefits of sex: mutational deterministic hypothesis or MDH. MDH postulates that sexual reproduction bestows an advantage by helping natural selection remove harmful mutations from the population.
University of Houston’s Ricardo Azevedo said: “According to MDH, in order for sexual populations to overcome the twofold cost of sex, two things must be true, the production rate of harmful mutations must be relatively high, such that each individual acquires on average one or more harmful germline mutations not inherited from its parents. The second is that these harmful mutations must interact in a special way, called negative epistasis, such that adding more and more harmful mutations makes your progressively worse off.”
2. Offspring are much different than parents
In species that produce asexually, offspring are the exact replica of their parents. Essentially, they just spread and multiply. But sexual reproduction is so much more different given that two beings are needed to form one offspring.
The offspring resulting from a union through sexual reproduction bears traits from each parents. It does make them similar, just not quite. In humans, a child may inherit his height from the father but the second child may not be too tall. In other words, the offspring produced differs all the time.
As mentioned earlier, this may help in terms of evolutionary changes. Science Daily, highlighting the University of Houston study above, stated “Sexual populations adapt better to their environments and become more resistant to harmful mutations,” but also added “but these advantages are more likely to benefit our natural enemies.”
List of Disadvantages of Sexual Reproduction
1. Reproduction late is slower
Asexual reproduction happens a whole lot faster compared to sexual reproduction. Since there is only one parent needed, the exhausting portion of finding the right mate is eliminated. This is a whole different world from reproducing sexually.
For one, species who reproduce sexually need to be able to find a mate in order to begin the process. For humans, that is the search for someone to be in a relationship with that will hopefully lead to the production of offspring.
Some animals, on the other hand, find the mating process quite tiresome. Take the walrus for example. Groups of males gather around a female vying for her attention. They make a variety of sounds for two purposes: a) to let other males know that they are eyeing a certain female, and b) they make these noises to get the attention of the female they are interested in mating with.
But it doesn’t just stop there. Since the mating season is long – lasting from December through March – males tend to get aggressive for the right to mate. Plus, they also consume less food during that period.
In short, it takes an enormous amount of effort in order to be recognized as a potential mate – true for the walruses and also true for the human species.
And when humans do get to copulate, normally only one child results from the union. Multiple births are definitely possible but the chances of a single birth are much more high.
Also, for humans and some animals, giving birth each year is not always an option – there’s almost always a gap between each offspring.
2. Reproduction is not always guaranteed
Lots of factors go into the successful creation of offspring. Meaning, not every act of sexual reproduction is guaranteed to produce an offspring. Some may try for years before anything fruitful comes out of the process.
Going back to the walrus example, females reach sexual maturity at the age of five to six years but don’t mate until later on. Males too are sexually mature at eight years of age, but start mating at 15 years of age because that’s when they are at their full physical size and are capable of competing for a female.