Sexual reproduction is the method by which living organisms produce offspring by combining the genetic information from two individuals of different sexes to create a new living entity. This process in most higher organisms involves the male producing a gamete that travels to fuse itself with a larger stationary gamete produced by a female.
In humans, this process occurs when a sperm fertilizes an egg. It may occur through artificial means, but it naturally happens after an intimate encounter with a male and female.
If fertilization occurs with this coupling, then a single-celled zygote forms with the genetic material from both gametes. Genetic recombination then occurs so that the DNA of the new cells aligns with each other to exchange information. Two more rounds of cell division occur to produce new cells with half the number of chromosomes from each parent. Human cells contain 23 pairs during regular sexual reproduction, which translates to 46 chromosomes.
Despite the numerous advantages that asexual reproduction represents, sexual reproduction continues to dominate the plant and animal world. It is one of the significant puzzles that scientists examine with this process. Even with this uncertainty, there are several advantages and disadvantages to review.
List of the Advantages of Sexual Reproduction
1. It creates a unique organism.
Because there are two parents involved in the process of sexual reproduction, there is a greater chance that evolution of the species will take place. The genetic information from each individual combine to improve the foundation of the offspring, creating an adaptive way to begin managing the challenges of new environments. This process allows animals to begin changing coat colors, specific traits to become emphasized, and other benefits that can ensure the survival of the species.
“I realized that nature had invented reproduction as a mechanism for life to move forward,” said Louie Schwartzberg, “as a life force that passes right through us and makes is a link in the evolution of life.”
2. This option reduces the risk of genetic disease.
If asexual reproduction occurs, then the offspring becomes a direct copy of the parent unless mutations occur during cell reproduction. That process is why scientists believe that it is a superior method to sexual reproduction, even if nature prefers otherwise. When only one parent is necessary to continue the species, then long-term survival is almost guaranteed. What you will find with this advantage is that the risk of spreading genetic disease is greatly reduced, even if one parent is a carrier, because the combination process uses the materials from both contributors to create a new organism.
3. It allows for genetic diversity.
Although there are times when complex animals can reproduce asexually even though they prefer sexual reproduction, it is not in their best interest to do so. The combination of two genetic material donations allows for there to be a higher level of genetic diversity, which is necessary to keep the general population of any species healthy. The times when it does seem to occur spontaneously are when females are kept isolated in high-stress environments.
4. This process reduces the threat of birth defects.
There is a theory where a solo human pregnancy would be possible if the stem cells from a female donor were coaxed into becoming sperm, which could then be implanted to form a zygote from one of her eggs. The price of doing so would be an extreme risk of a genetic bottleneck that a timebomb would occur for the survival of the species. Even limited interactions with family intermarriage create physical problems and birth defects that don’t occur as often when there is genetic diversity.
Prince Charles II of Spain was the last Habsburg ruler of the Empire. Because the royal families of Europe stayed in such a tight-knit group, a defect called Prognathism occurred where the lower jaw juts out prominently. Prince Charles had such a bad case of it that he couldn’t even eat correctly.
5. It can purge harmful mutations from future generations.
Sexual reproduction is more efficient in its process of removing harmful mutations from the general population. Although there will be offspring who do not survive because of the birth defects they encounter, it is an advantage that protects the future of that species. Even when both parents are a carrier for a specific disease or condition, the rate of transference is typically 50%.
Even when there is a severe issue, such as the Gaucher gene in the Ashkenazi Jewish population, that person could have offspring with a partner who is unaffected by the issue. This outcome would create carriers, which could then be tempered in the next generation by mating with another unaffected person. Even if two carriers produce offspring, the risk of Gaucher disease is just 25%.
6. Sexual reproduction can help to select beneficial mutations.
Scientists believe that there are four beneficial evolutionary mutations that are occurring in the human race right now. People who have the Apo-AIM gene have significantly lower levels of risk for a heart attack or stroke than the general population. A family in the U.S. Midwest has a mutation of the LRP5 gene that amplifies bone density to have the skeletal system be stronger and denser than average.
Italian researchers discovered in 2001 that population groups in Burkina Faso had a variant of hemoglobin that they called HbC that allows someone with two copies to have a 93% lower risk of developing malaria after being infected. And then theoretically, women could have a mutated gene in her color receptors that would give her four different ones instead of the standard three.
7. It works to ensure the survival of the species.
Species that use sexual reproduction as a method of producing offspring use hormonal perception as a way to locate superior physical specimens for mating. Humans encounter this advantage as well. Have you ever felt immediately attracted to someone even though they were a stranger? One of the reasons for that reaction is because your body instinctively felt like it would “click” well with that other person.
When two parents with superior traits combine genetic material to create offspring, then this advantage works to ensure the survival of the species. The best traits get passed to the next generation because of this process.
8. This method of reproduction can improve immune resistance.
When there are higher levels of genetic diversity within a species, then the general population receives a higher level of disease resistance. There are always particular people who can resist a virus, bacteria, parasites, and other dangers to personal health because of the variations that are present due to sexual reproduction. If parents could clone themselves using asexual methods, then it would increase the risk of an adverse event that could threaten an entire species.
9. Sexual reproduction is usually a rewarding experience.
Although you might regret that date on Tinder from the other day, the processes of sexual reproduction are designed to be pleasing and addictive to encourage this activity. Humans have a drive to have sex because the process of mating releases high levels of dopamine in the brain. That is why it is typically a rewarding experience. Frequent encounters with a trusted partner can create an effect that is similar to that of an antidepressant. It can act as a pain reliever thanks to higher oxytocin levels, improve memory, and it provides you with some exercise as well.
10. Ongoing sexual reproduction results in brain cell development.
People who have sex frequently can experience an enhancement to the processes that grow brain cells. Research from 2010 out of Princeton found that when animals or humans are sexually active repetitively, then they experience more brain growth compared to those of their species who are more abstinent. This advantage focuses on the hippocampus, which is the area of the mind where memory management occurs. When there are more connections there, larger cells form, and that encourages a greater frequency in mating behaviors.
11. Sexual reproduction can provide some unique health benefits.
Human males who have sex about 1-2 times per week are less likely to develop heart disease compared to those who only have intercourse about that many times per month. Everyone experiences lower blood pressure over time with ongoing sexual activities. There can also be reductions in cortisol levels, which indicates there is less stress and inflammation happening in the body at that time.
Sexual reproduction can also promote a stronger immune system, improve muscle strength, and can lower the risks of specific cancers. Although there is a higher risk of disease transmission with this activity, safe sex practices can help to limit that problem.
List of the Disadvantages of Sexual Reproduction
1. Less than 50% of the population is capable of gestation.
Sexual reproduction allows a majority of females of child-bearing age to participate in gestation with this method. Males do not generally bear their young, although Mother Nature does have some examples where that option is possible. Individuals who show characteristics of both genders (or no gender) may not have the capability of participating in this part of the reproductive process. That means there is a significant risk to the survival of the species if one or the other sexes is in limited supply.
“The reproduction of mankind is a great marvel and mystery,” said Martin Luther King, Jr. “Had God consulted me in the matter, I should have advised him to continue the generation of the species by fashioning them out of clay.”
2. It requires each gender to find a mate.
Asexual reproduction allows a parent to have a child when the time is right for that process to occur. Sexual reproduction requires the finding of a mate. If one is not found, then it is not possible to produce offspring. Humans work around this issue by creating genetic donation banks where single parents can pursue having a child, but it still requires the use of a surrogate or donated gamete to create the offspring.
Parthenogenesis occurs in nature quite often, including with complex animals like sharks and lizards. We also know that, with assistance, stem cells from female donors can be induced to grow into sperm cells.
3. Outside influences can determine offspring viability.
Because asexual reproduction occurs immediately with a direct genetic transfer, there is a lower risk that the pregnancy will not be viable. There are outside factors that can influence the processes of gestation with sexual reproduction so that a healthy offspring can still develop unwanted changes to their genetic profile. Mothers who drink alcohol during their pregnancy, continue to smoke, or fail to consume enough folic acid can make their otherwise healthy children develop physical or mental disabilities that could impact their entire life.
About 3,000 newborns every year have neural tube birth defects that are directly attributed to a lack of folic acid each year.
4. Sexual reproduction can transfer diseases to another individual.
Sexually transmitted diseases have a profound impact on the reproductive health of any species. More than 1 million new STIs are acquired each day around the world in the human population. There are over 370 million new infections of four common infections: trichomoniasis, syphilis, gonorrhea, and chlamydia. About 500 million people have an HSV genital infection, while 290 million women have an HPV infection.
The problem with STIs is that many of them have zero symptoms. If a flare-up does occur, then the unwanted side effects might not be recognized as an STI. In 2016, there were almost 1 million women infected with syphilis during their pregnancy, resulting in about 350,000 adverse birth outcomes – including 200,000 newborn deaths or still births.
5. This option for reproduction is not guaranteed.
Couples who are trying to have a child may say that they’re having fun with the process because of the advantages of sexual reproduction, but it is also reflective of this disadvantage. You can do everything correctly, even at the optimal time to create a pregnancy, and not have the result that you want. People and animals can sometimes choose infertile mates, limiting their opportunities to have offspring. The gametes may not fuse together either.
According to information published by RESOLVE, 1 in 8 couples will have trouble either getting pregnant or carrying their pregnancy to term. That means about 12% of women will face this disadvantage at some point in their life.
6. There are health conditions that can interfere with sexual reproduction.
Having an STI or STD can interfere with the processes of sexual reproduction, but there are other health issues that can be problematic for this condition as well. Women who experience ovulation problems like PCOS or POI may find it challenging to produce an offspring, which is a factor in over 30% of couples who try to conceive. Blocked fallopian tubes can prevent an egg from meeting a sperm as well.
Male infertility is an issue with sexual reproduction too. This issue is a factor in 8% of couples who want to have a baby. There are also unexplained reasons for infertility that impact about 10% of couples.
7. The best genetics don’t always get sent on to the offspring.
In reference to the example with the Ashkenazi Jewish population group, someone with Gaucher disease who has an intimate partner who is a carrier will have their offspring with a 50/50 chance to have the condition passed along. If two people who are carriers have children, then there is a 25% risk of this health issue for boys.
This population segment also features four other diseases that occur with greater regularity than in the general population because of mutations and high carrier frequencies: cystic fibrosis, Tay-Sachs disease, familial dysautonomia, and spinal muscular atrophy.
8. Sexual reproduction results in fewer overall offspring.
Asexual reproduction occurs with greater frequency and better certainty, which is why it is so often seen as a better option for species survival from a quantity-based standpoint. Sexual reproduction encourages greater quality in the genetic profile, but there are usually lower population numbers because of that trend. The most common birth for humans is a single child, even if there is an increase in multiples. Smaller animals tend to have larger litters, but even they can’t beat the numbers that come from the asexual process.
9. It can be deadly to participate in sexual reproduction.
Up to 5% of the human population in the world today has a brain aneurysm, with many of the individuals not realizing that they have this health issue. There are eight triggers that can cause an aneurysm to rupture, and sexual activities are one of them. When people have sex, there is an increase in their blood pressure that can cause this area to begin leaking into the surrounding brain tissue. Only 1 in 4 people who experience this issue will survive without any permanent disabilities.
This trait is found in many animal species too. Although the rates of aneurysm or heart attack might be lower, this risk is rarely an issue when the focus is on asexual reproduction.
Conclusion of the Advantages and Disadvantages of Sexual Reproduction
Sexual reproduction offers several advantages that are worth considering, especially from a long-term evolutionary view. It may not be as efficient as other methods, but sexual reproduction seems to be Mother Nature’s preference because of its genetic filtering action. The survival of any species using this method is much higher than that of asexual methods.
There is always some level of risk to consider with having offspring. Pregnancy-related deaths are at their highest rate in the industrialized world in the United States, with about 700 women because of delivery complications or health issues that result from the body’s changes. A healthy pregnancy begins before conception.
The advantages and disadvantages of sexual reproduction show us that this method of natural selection may allow some individuals to out-produce others because of their ability to secure mates. That makes it easier for the strongest genetic material to become the foundation of the next generation, even if there are some instances when intercourse doesn’t lead to the creation of any offspring.
Crystal Lombardo has been a staff writer for Future of Working for five years. She is a proud veteran and mother. If you have any questions about the content of this blog post, then please send our editor-in-chief a message here.