Reasons Why Evolution Is True Part VII:
Coevolution

Few species go through life without interacting with an other, but some interactions are more intimate than others. Pollination is an example of an interaction that, in some species, has become very intimate indeed! Most dedicated pollinators show adaptations to this, such as pollen baskets in bees, but these are often generic adaptations that enable the individual to visit many different species of plant. Equally, plants have adaptations to attract a variety of different insects. Different pollinators (bees, birds, moths) have different visual systems, and thus different flower colouration can be used to attract pollinators of different species. The timing of flower and pollinator emergence is also carefully timed in order to ensure maximum cross-over between the two. Pollinators generally gain food from the relationship, whilst plants achieve dispersal of their genes without having to physically move themselves.

Some plant-pollinator interactions are more intimate, more specific. This can lead to more extreme adaptations, as the two species become increasingly specialised for interacting with one another. Possibly the most extreme plant-pollinator relationship exists between the fig and the fig wasp. Young fig wasps emerge as larvae inside a tiny fig. The larvae feed on the fruit of the fig until they are ready to mature into adults, which again occurs within their fig prison. As adults, the wasps mate, collecting pollen from their birth fig before they leave. The male fig wasps then dig their way out of the fruit, creating a path for the females to emerge from. The male fig wasps are not well suited to life outside the fig, however, and often die shortly after making their escape. The females fly off and find a new fig plant where they can lay their eggs. Squeezing through the tiny entrance hole, known as the ostiole, the female enters a new fig and deposits her eggs inside the fruit, simultaneously depositing pollen on the fig’s reproductive parts.

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What Makes Us Human Part I
A Brief History

The earliest known hominid was Sahelanthropus tchadensis, represented only by relatively few fossilised skull fragments, he is so ancient it isn’t clear whether he could truly be considered human at all. Fossils found in Chad, dated to around 7 million years old, may have belonged to a direct human ancestor, or more likely to a neighbouring branch of the ape family tree. This uncertainty is common until around 4 million years ago; many species are known only by partial skeletons and the relationships between them are often unclear. The Australopithecines may be the first group of hominids that we can be said to understand to any extent.

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Reasons Why Evolution is True Part VI:
Homology

Although it makes sense to stick with a good idea when you’ve found it, you wouldn’t stubbornly stick to the same design even when it wasn’t quite working properly, would you? And yet this is just the pattern that appears in nature. Life on Earth shares a remarkable list of features, from protein-handedness and membrane structure to the DNA code. While some of these features, such as protein-handedness (which way around proteins are formed), are inconsequential, others are not. The genetic code is almost completely universal across all life. This is the reason GM can work, because a gene coded for in the genome of one species can be read by the translation machinery in another species’ cells. This does not necessarily have to be true, however, as the code is arbitrary and there are many possible configurations which would work equally well. Furthermore, the code is actually detrimental for some species living in extreme environments, since certain codes are more volatile than others. Despite this, the code is shared by all.

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What Makes Us Human?

Understanding the evolution of Homo sapiens, and how humans came to be human, has been a fascination for people since Darwin’s time, but it has also proved to be one of the most controversial of the sciences. Humans and Chimpanzees diverged about 7 million years ago and during this time a great deal of anatomical and behavioural changes occurred which now distinguish us from our closest relatives. Despite this, we still share over 99% of our genetic make-up with Chimpanzees; only 1% of our genes truly make us human. What is the manifestation of this 1%? Some of these differences are very clear visually; we are taller and less hairy, with larger brains and an upright, two-legged stance. Other differences are slightly more subtle; we have language, we use tools, we have culture and art enabled by abstract thought, we have a concept of self… but as that list continues, it becomes increasingly difficult to determine whether Chimpanzees, or indeed other animals, also share these qualities. If Chimpanzees can be taught language, then this indicates they have a brain capable of understanding and learning language, and thus, surely they can in some sense be said to have language themselves? Other characteristics are even more difficult to pin down; how do you measure self-awareness? Although there is a long list of traits that most people would consider to be exclusively human, the situation is in fact far less clear cut than that.

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Reasons Why Evolution is True

Across the next 10 articles, I present a few of the quirky examples of evolution that we can readily observe in nature. It is by no means an exhaustive list, but merely a set of stories which I feel illustrate well the power of evolution to create complexity, and how we can see evidence for natural selection by looking carefully at the idiosyncrasies it has produced.

The examples I provided in this series can be broadly categorised into a few themes; coevolution (Fig Wasps and Hawk Moths), evolutionary constraints on adaptation (Pandas, The Human Eye), convergent evolution (Birds and Bats), adaptive radiation (Galapagos Finches, Ring Species) and homology (DNA and the Pentadactyl Limb). And within each of these categories, there are numerous other stories I could have told to illustrate my point. But the point I am trying to illustrate is that evolution is a real phenomenon. Charles Darwin’s theory of evolution by natural selection is one which explains the natural world around us in both a satisfying and verifiable way.

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Ants: Civilisation in Minature III

Crime and Punishment

Ant societies are remarkably complex and ants exhibit extremely high levels of cooperation. Workers will often sacrifice their own lives to defend the safety of the nest. However, just like human societies, ant nests are also rife with conflict. Where there is cooperation there will always be individuals who try to take advantage and cheat the system.

The defining characteristic of ant colonies (and social insects in general) is reproductive division of labour, where reproduction is dominated by one or a few individuals, known as queens. In this matriarchal system, reproduction is forbidden for most colony members, and in many ant species worker ants are physically incapable of mating. Despite being unable to mate, due to their unusual genetic system, ant workers can still lay male eggs. This gives them the opportunity to try and cheat the system, and in many ant species workers have been found to illicitly try and lay eggs, when the queen isn’t looking. Such crimes do not go unpunished, however, and in many species the honest workers will punish cheaters, either through physical aggression, or by destroying the illegally laid eggs.

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Reasons Why Evolution is True Part V:
The Quirky Human Eye

The mammalian eye, a refractive cornea non-compound eye, to be precise, is a wonderful example of the bizarre quirks of evolution that we see in nature. These are only really bizarre, of course, from the view-point of intelligent design.

Our visual system is made up of many tiny light receptors on our retina known as rods and cones. Each receptor picks up a small portion of light and relays the message to our brain via nerve connections in the optic nerve. Information from thousands of light receptors is pieced together by the brain to form an image of the world around us. The rest of the eye is designed to focus light onto the retina in the most efficient way possible. Logically, you would expect, therefore, that the eye would be designedso that nothing blocked light from reaching the retina. And yet, in the mammalian eye, the nerves and blood vessels connecting to the rods and cones protrude outwards in front of them. In order to connect back to the brain, the nerve fibres must then break through the wall of light receptors, creating a blind spot where they join the optic nerve.

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How to Read a Mind

Mind reading no longer exclusively belongs to the domain of science fiction writers and mediums. Over the last 50 years, researchers around the world have been working on a system known as the brain-computer interface (BCI) which allows direct communication between the brain and an external device such a computer or a robotic limb. The main goal of this research is to develop technology capable of restoring sensory function to the blind or deaf, and restoring movement to patients suffering from paralysis. Major strides have been made in this endeavour over the last decade, and BCI technology is now even being adapted to commercial purposes such as gaming.

BCI technology is possible because of the way in which the brain transmits messages within itself and to other areas of the body. The brain is composed of around 100 billion cells called neurons. Messages are sent from neuron to neuron as an electrical impulse, created by ion imbalances in neuronal membranes. Neurons are insulated by a coating known as the myelin sheath, which prevents most, but not all, of these electrical impulses from escaping. The tiny portion of the electricity which escapes from the myelin sheath can be detected and this signal can be interpreted by computers. A second feature of the brain is also key to the success of BCI: neural plasticity – the ability of the brain to adapt to new situations. Patients suffering with brain damage illustrate neural plasticity; in many cases patients are able to, over time, adapt other areas of their brain to perform the tasks of damaged regions. Neural plasticity also enables the brain to adapt to interpret new input, such as that provided by the brain-computer interface.

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Ants: Civilisation in Miniature II

Agriculture
They might seem simple and insignificant, but like humans, ants have discovered the benefits, and costs of agriculture. In the ant world there are species which farm livestock, protecting them from predators and milking them for rich nectar, and others which cultivate tiny underground fields of fungus, pruning it and using chemicals to prevent disease and pests.

Crops and Livestock

Humans developed farming around 10,000 years ago, but the ants have been at it much longer. In its simplest form, ant farming consists of simply pruning the surrounding forest. Ants of one species found in the Amazonian rainforest have been found to remove unwanted plant species when they appear in its foraging area. Although simple, this ‘weeding’ behaviour can be devastating, with ants clearing huge sections of forest of any species which is not beneficial to them.

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