Reproduction, the passing on of our genes to another generation, is life’s most important task. As decreed by Nature, it is the very purpose of our existence.

And yet, all species have limited opportunities for reproduction. An individual has to reach a certain level of maturity; they may have to wait until the environmental conditions are amenable for their off-spring’s survival and they will have a limited fertility or reproductive lifespan.

That’s why – with such limited opportunity – they need to get it right; they need to do the best that they can. They need to maximise their genetic potential.

Individuals in seeking to secure the on-going future of their genes endeavour to achieve a two-fold task: they need to ensure that their genes are passed on to the next generation and, secondly; they need to ensure that their genes are in a better and stronger position in relation to their environment than they were previously.

Achieving the first part of this objective – genetic survival – is their basic aim; achieving the second – genetic enhancement – is a bonus.

In striving for this, the most important element of ensuring successful reproduction is the choice of reproductive partner. Who is an individual going to mate with? Whose genes are going to be mixed together? Which genes are going to be more dominant?

In selecting a reproductive mate, some will choose a partner for life; some will have a new partner each season; some will even have multiple partners.

Finding and mating with a desirable reproductive match is not always straightforward; there’s no certainty that a pairing will be ideally matched; there’s no guarantee that a particular pairing will be genetically fruitful.

There are, however, environmental conditions and species behaviours which may favour more advantageous partner selections:

Ample Choice

When there is choice it means that individuals have options. There are different directions that can be pursued. In selecting a reproductive partner, an individual will choose from the different genetic qualities that may be available. Some qualities will prove more attractive than others. The individual will have an opportunity to promote those qualities which it believes are the most desirable, most beneficial and most viable. The more choice there is then the more genetic opportunities there are.

For a species to prosper there must be diversity within that species. It improves their survivability and enhances their potential. A successful species tends to be characterised by a highly diverse genetic make-up.

Pandas are a classic example of a species that has entered a spiral of decline caused by their loss of habitat but which, as their numbers have diminished, has significantly exposed their vulnerability due to a lack of genetic diversity.

Abundance of Supply

The more plentiful the supply of potential reproductive partners then the more confident an individual will be with regard to finding a desirable partner. They don’t necessarily have to accept the first prospect that comes along. They can be choosier and, as a consequence, perhaps improve their chances of making a more advantageous selection.

Some species will seek to take advantage of this by collecting in mass gatherings in order for partner selection and reproduction to take place. This not only ensures that they have more choice but also that they can – individually – choose a partner that they are most attracted to.

Lekkings, gatherings of males in clusters to competitively show off to females, are a good example of this free market mating behaviour.

Mutual Selection

This is when males and females agree that their match is a mutually beneficial one. They have singled each other out, both perceiving some genetic advantage to be gained. This match-making can often be determined through various mating rituals.

The fact that both genders have some involvement in the selection process means that the pairing is more likely to be successful – two minds being better than one!

This contrasts with instances where one of the genders foists themselves on the other. In such circumstances, any genetic advantage may be very one-sided.

It should perhaps also be noted that mutual selection and agreement may not always be a conscious decision on the part of both genders – many females, for instance, may instinctively, unquestioningly accept the strongest or biggest male as their partner.

Time

The more a species can devote itself to its reproductive purpose and the selection of a partner then the better it will genetically fare. Even though reproduction may be a species’ main priority, not all species are able to commit totally to it. Some species in certain harsh and threatening environments may have to devote themselves to other aspects of their existence – such as finding food or avoiding predation – just in order to survive. This means that their reproductive priority has to be diminished.

Therefore the more successful species tend to be those that have some dominance or control over their environment. It means they have more time to commit to finding the best reproductive partner.

Positive Choice

Genetic advancement is most likely assured when individuals make a positive selection when choosing their partner. It is far better for an individual to choose what they want rather than to merely accept what they can get.

It’s like ordering from a restaurant menu; you’re more likely to be satisfied with your meal if you pick what you want rather than letting somebody else order for you or accepting a meal because that is all the restaurant has available.

And yet, within some species, individuals will take what is given rather than necessarily seeking out what is best. In such circumstances, it becomes more a partnership of convenience rather than a plan for development. Sometimes, of course, they may have no choice about this.

Similarly, if two partners reproduce merely because they are in the same place at the same time this does not necessarily mean that they are best suited to one another. A species that relies on fortuitous encounters to find a reproductive partner will have less promising success at securing their genetic advancement.

This would be of particular relevance to solitary animals such as leopards or polar bears who roam across vast areas. They may not always be in the right place at the right time to find their ideal reproductive partner.

Of course, chance encounters can work both ways. When an individual has to take what comes along rather than seeking out what is wanted, that can sometimes prove advantageous – when you have to take what’s there, sometimes you can get more than you deserve. There may be a “swings and roundabouts” element to this, with the overall result balancing itself out.

Level of Competitiveness

The more vigorous the process of selecting a reproductive partner, then the better a species’ chances of improving its genetic stock. The harder it is for an individual to secure their choice of reproductive partner then the more they have to prove themselves, the more they have to demonstrate their genetic worth.

The more challenges an individual overcomes whether that be from intra-species rivalries or from the environment – including other species – then the greater their genetic strength and therefore the greater their genetic desirability. The tougher it is to be a dominant individual then the better that individual must be. This is why, for many species, aggression and fighting is a fundamental part of the courtship and mating process. Individuals are seeking to prove themselves. It should mean that only the best genes are passed on.

When considering reproductive partner selection, these aspects are critical to the maximising of a species’ genetic outcomes. The more a species can meet these criteria – demonstrating commitment, involvement and focus – then the more they should genetically prosper.

However, there are a couple of further considerations which may mean a species can survive and can even achieve genetic progress without adopting some or all of these methods. This is because of the following:

Firstly, some environments are more challenging and more changeable than others. Some, in fact, are in a constant state of flux. It is in these environments where partner selection is the most critical. Given that the surest way to a species’ decline and possible extinction is for that species to be out of kilter with its environment, a species’ genes need to respond to that changing environment. The more a species is able to respond then the better its chances of survival.

If, on the other hand, an environment is relatively static then the pressure on genetic development and thereby on reproductive selection will not be as great. Genetic change does not need to be so driven and individuals can perhaps be less selective in choosing a partner.

Secondly, within a species, many evolutionary advances come from some genetic mutative activity rather than through the enhancement, strengthening or concentration of existing genes. A species can therefore make significant genetic advances by chance. In such occurrences, it does not necessarily matter whether or not the reproductive partners have been optimised.

It may well be that in some species this higher level of mutative activity is more prevalent or more pronounced. As such, partner selection becomes less significant. So long as reproduction is taking place then the genetics adaptations and advances will naturally occur.

In Nature, a species will pursue its own particular partner selection process because it has been found to work. It manages to achieve desirable outcomes. If it didn’t, then that species would have failed or it would have had to devise a different selection strategy.

However, the question that always needs to be asked but can never be properly answered, is whether or not that which is being pursued is a species’ most effective strategy? Are there more substantial genetic gains that could be made if a species adopted a different approach to partner selection?

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