Reasons Why Evolution Is True Part VII:

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?

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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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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Ants: Civilisation in Miniature II

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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Ants: Civilisation in Miniature

You might not think you have much in common with the small, six-legged creatures that occasionally break into your home to raid jam jars, but over the next three articles I hope to illuminate some of the parallels between people and ants. Like humans, ants are highly social; building civilisations, utilising sophisticated mechanisms of communication, and nurturing other living creatures in various forms of agriculture. And just like us, their societies are sometimes compromised by cheats and criminals. Ants share many of these traits with other members of the social hymenoptera, which includes most bees and wasps. Few species outside this group have developed cooperation as sophisticated or complex.
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Reasons Why Evolution is True Part IV:
Galapagos Finches

For most biologists and reasonable people, evolution is FACT. In as much as gravity could be said to be fact. However, for those who deny the existence of evolution, the difficulty of observing its occurrence in real time is proof enough that it doesn’t exist. There are a few key examples of evolution in action, however, and during these short essays I have been detailing some of them. One of the most famous examples is that of the Galapagos Finches, which inspired Darwin as he formulated his ground-breaking theory.

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Reasons Why Evolution is True Part II:
Parasitoid Wasps

Parasitoid wasps are a little known, but extremely prolific group of wasps, who provide one of the best examples of evidence for evolution that I’ve come across. Parasitoid wasps have a particularly gruesome way of life. They make a living by laying their eggs inside the larvae of another insect, often a caterpillar. As the young wasp develops, it devours the host from the inside out, eventually emerging and killing the host.

Parasitoid wasps are found in 37 different families of a single order, the Hymenoptera, which contains all bees, wasps and ants. There are thousands, maybe even millions of species of parasitoid wasp, each preying on a different host, utilising a different set of tactics to subdue their victim. Many parasitoid wasps are considered to be beneficial to humans because they kill garden pests such as aphids. But this is not the important part of the story.

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Reasons Why Evolution is True Part I
The Panda’s Thumb

Pandas are crap. They might be cute, cuddly and charismatic, but the simple fact is that they’re really pretty rubbish at being pandas. You might think that being good at being a panda would be a fairly important trait for a panda to possess, but sadly these beautiful animals are victims of evolutionary history. Giant pandas are members of the bear family, and they evolved from a common ancestor with other bears during the late Pleistocene, approximately 600,000 years ago. Bears are members of the Ursidae family, within the order Carnivora, and as the name suggests, almost all bears are meat-eaters. That is, except the panda. Bears have evolved a club-like paw, with limited independent movement of their digits, which is excellent for attacking live prey. Pandas, having evolved from a carnivorous, bear-like ancestor, share this adaptation, despite no longer eating meat. Bamboo is particularly difficult to grasp without a thumb. And Pandas need to consume an awful lot of bamboo to survive: about 40kg every day.

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Frogs Develop Biological Anti-Freeze

While most animals will try to avoid freezing at all costs, some species of frog are actively encouraging it.

The wood frog (Rana sylvatica) is one of a handful of freeze-tolerant animals with adaptations to cope with freezing for up for 4 weeks. And within hours of defrosting the frogs are back to their usual selves again.

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