A giraffe gracefully extends its long neck, reaching high into the branches of a tree to pluck leaves with its prehensile tongue. Its legs are firmly planted on the ground, supporting its tall frame as it stretches to the uppermost leaves. The giraffe’s elongated neck and legs are such unique adaptations that allow it to access food sources that other herbivores cannot reach.
Giraffes have such a distinctive frame, but they weren’t always like this – according to Charles Darwin. He used giraffes to illustrate the concept of natural selection, which can be summarised as “survival of the fittest.” He believed that giraffes with longer necks had an advantage over others, as they could reach food that was high up in trees, giving them an edge in survival and reproduction over giraffes with shorter necks and other animals.
What is Natural Selection
Natural selection is the process by which certain traits become more or less common in a population over time based on their effects on the survival and reproduction of the individuals that possess them. The theory of natural selection was first proposed by Charles Darwin in his 1859 book “On the Origin of Species.”
In the book, Darwin explains how natural selection works and how it can lead to the evolution of species over time. He argues that organisms with traits that are beneficial for survival and reproduction are more likely to pass those traits on to their offspring, while organisms with less beneficial traits are less likely to do so.
As a result, the population gradually changes over time, with the traits that are most beneficial for survival and reproduction becoming more common. This process, Darwin argued, could explain the diversity of life on Earth and how different species have evolved over time to best suit the environment that they occupy.
Darwin’s theory of natural selection was met with scepticism and controversy at the time of its publication, but it has since been supported by a wealth of scientific evidence and is widely accepted as one of the foundational principles of modern biology. I am extremely interested in the theory of natural selection, and how it goes further than just changes in physical traits in animals.
Today, there are three surviving elephant species; the African savannah elephant, the African forest elephant and the Asian elephant. More than 160 extinct proboscidean species (mammals with traits such as the trunk, tusks, and a large form), have been identified from fossil remains found on each continent except for Australia and Antarctica. Originating from Africa, the first proboscidean, the Moeritherium, had no trunk and existed around 40 million years ago. The trunk initially evolved in order to serve these animals as a snorkel, and now in modern-day elephants for assistance in gathering food.
It’s easy to talk about a giraffe and its long neck, but I wanted to try and see if there were other changes that are harder to discern. I have jumped further into two examples of species that have evolved specific traits through natural selection at Londolozi and how they are a great example that this theory is not just about physical changes and does not only apply to animals.
Not just physical changes: Leopards and their behaviour
When we talk about natural selection, we often talk about how animals have changed physically to adapt to their surroundings and competition. However, it’s not just physical traits that can change – behavioural traits can also change. Take, for example, leopards. A study conducted in the Sabi Sand in 2017 talks about how leopard mothers have adapted to favour cub survival over reproductive output.
Leopard mothers typically give birth to two to three cubs per litter. They take care of their cubs for an extended period, between 9 to 35 months. Studies suggest that this prolonged care period may have evolved as a way to increase the survival and future reproductive success of the current offspring, even though it reduces the mother’s opportunities to have more litters over her lifetime. Research has shown that this prolonged care can significantly increase the cubs’ survival rate, which is important as fewer than 40% of cubs reach independence.
Not just animals: Acacia Trees
The plants at Londolozi have also evolved through natural selection. For example, the acacia tree has evolved to have thorns, which protect it from herbivores and increase its chances of survival and reproduction. Acacia trees are a prime example of how natural selection can shape the evolution of a species. These trees have evolved to have thorns, which serve as a defence mechanism against herbivores that might try to eat them. These thorns deter animals from eating the tree’s leaves, branches, and fruits, which increases the tree’s chances of survival and reproduction.
This is in line with Charles Darwin’s theory of natural selection, which states that organisms with traits that are beneficial for survival and reproduction are more likely to pass those traits on to their offspring, while organisms with less beneficial traits are less likely to do so. As a result, over time, the population gradually changes and the traits that are most beneficial for survival and reproduction become more common.
Overall, natural selection is the process that drives the evolution of species and shapes their characteristics over time to adapt to their environment. Regarding leopards and their behaviour, mothers are now evolving to take care of their cubs longer resulting in fewer litters produced in their lifetime to ensure the survival of the cubs they do have. We see the natural selection with plants as well, and one of the best examples is acacia trees, where the traits of those with thorns have been passed down.