The term survival of the fittest is attributed to Charles Darwin but was made by Hebert Spencer. However, Charles Darwin was one of the first people to notice that animals that adapted to their environment had a better chance of survival, and nature plays a large part in this.
To ensure the survival of a species, the best genes need to be passed down to future generations. Most animals go into heat which is a receptive fertile state, only allowing them to get pregnant at this time. Males will often compete to mate with females, ensuring the most dominant genes are passed on. Females will often resist the advances of males unless they believe them to be the best suitor.
It is usually a male’s display of power and strength or the largest horns or antlers that show females that they are the best mate for them. These adaptations flow forward in their genes, enabling these to be pushed forward into future generations. These adaptations evolve the species as a whole to ensure maximum survival. In these cases, it is the survival of the fittest.
Monogamy vs polygamy
Monogamous animals are animals that only breed with one partner at a time. Monogamous animals that mate is usually those with the best genes and showing the best adaptations. These are also generally the most dominant, and it is these animals will breed, passing on their genes to the next and future generations. Animals that are not as dominant may not get the chance to mate and will not pass on their genes.
This results in the best genes being passed forward and is most common in animals with a social system where there is a dominant male and female, such as wolves. The dominant male and female achieve their position from competition within their groups.
However, most animals are not monogamous. Most animals are polygamous, meaning they mate with more than one partner. Polygamy is an excellent way for a species to thrive to ensure survival. However, this does have its downsides. By not being able to select the best partners, they cannot hope to pass on the best genes. In most animals, survival is linked to reproduction, and reproduction for males is a measure of success, no matter who it is with.
What happens when an animal goes into heat?
Heat or oestrus is a state of receptivity for female animals where they are most attractive to males who want to reproduce. Humans do not go into heat as they have a menstrual cycle. There are four cycles in the entire breeding cycle.
- Pro-oestrus – This is when the follicles of the ovary start to grow. This period can last for 4-20 days and causes the uterus lining to develop, which the egg will attach to.
- Oestrus – Oestrus occurs when the animal is sexually receptive, also known as in heat. Ovulation occurs or is induced by copulation.
- Metoestrus – This brings the fertile stage to a close, and the animal is no longer fertile. This can last up to 2 or 3 months.
- Dioestrus – This is the resting stage, and the animal is infertile.
How nature delays the spread of inferior genes
Nature has a way of stopping all sexual acts causing reproduction and potentially passing on bad genes. Young, immature males cannot impregnate females until they are mature enough. This allows the older, superior, dominant males to reproduce with the females, passing the dominant genes forward.
Some ways that nature stops the spread of inferior genes is by delaying the chance of getting pregnant until the last few hours of estrus or by the female not being receptive to male advances. Large fights can also occur between groups of males for the most dominant one to be chosen.
In polygamous animals such as hippos, deer, gorillas, and wrens, females will resist the attempts from the males for some time. Elephants are masters at this, with the females running off while the male chases them. When the male attempts to mount them, they will run off again before returning to the herd. This can go on for a few weeks, and in that time, larger, more dominant bulls may come into the herd. This is another way that nature makes sure that the best genes get put forward to future generations.
In some animals, ovulation, the production of the egg, does not occur automatically. One method is called induced ovulation and occurs in animals as varied as koalas, cats, and bears. This delays the female from getting pregnant until they have found a proper suitor.
While many animals have cyclical ovulation, induced ovulation only happens after the animal has repeated copulation. In the case of cats, this can occur up to 100 times over 3 or 4 days. By doing this, cats are showing that they have stamina and power, significant advantages that can be passed on to the next and future generations. As this takes place over several days, the male cat will also have to fight off advances from other male cats who pick up the scent of the female in heat. Whoever is still standing at the end will be able to pass their genes forward.
Antelopes such as kudu attract males in heat for only 2 or 3 days of their cycle. The males will spar with each other for the right to mate. Positive selection is almost guaranteed for the male left as the female-only ovulates for the last 6 hours.
In this article, we have looked at how nature ensures that the best genes get put forward to future generations. This ensures that the best adaptations also get put forward, allowing the evolution of the species and the survival of the fittest.