Category: Biology

Human origins

Theorists can move forward again – and the picture seems a little more complicated than we thought.

Where did we come from, and how? We’ve long thought in terms of an evolutionary ‘tree’, but our origins in Africa are more like a braided channel. This idea provides a better fit to the data.

Based on fossil evidence alone, studies of human evolution have long agreed that modern humans evolved in east Africa and radiated out from there. But with the development of cheap, fast and reliable DNA evidence from modern populations, and DNA from fossil teeth and bone samples, it’s becoming clear that theorists can move forward again – and the picture seems a little more complicated than we thought.

Human dispersion, events described in the article all took place in Africa – Image from Wikimedia

On 17th May, Ragsdale and others published a research paper in Nature; ‘A weakly structured stem for human origins in Africa’; their evidence suggests evolutionary connections in populations that were separated for a while before recombining. So instead of an evolutionary tree (which most people were expecting) it seems that our human past is more like a set of braided channels.

Previous views on human evolution proposed a tree structure (branching but not recombining). However, the new ‘weakly structured stem’ model fits the data better than a tree model. It also explains the diversity of genetic forms in modern human populations, and shows that there is no single place in Africa where humans ‘originated’. After this process within Africa, humans spread out as show in the map.

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Elephant hawk moth

The caterpillar did something extraordinary – it mimicked a small snake

Have you ever seen an elephant hawk moth? If you live in Europe or Asia you might have spotted one of these amazing insects. In the United Kingdom they are fairly common, but perhaps not often seen. It’s a real treat to spot an adult or a caterpillar, both are amazing sights.

An elephant hawk moth male (credit: Wikipedia)
The circle marks the spot (credit OpenStreetmap)

Walking in the Cotswold Water Park recently, near the Gateway Centre on Lake 6, we spotted an elephant hawk moth caterpiller crossing the footpath (close to the grey circle in the map.

For a short time we just watched as it made its way across the path. But before it made it to the vegetation on the far side, some people appeared with a dog. The dog ran up enthusiastically to greet us and accidentally kicked the caterpiller before running off again. The caterpillar did something extraordinary – it mimicked a small snake.

Am I a caterpillar, or am I a snake?

The caterpillar crossing a stony path

For perhaps 20 seconds or so it writhed its body in a convincingly snakelike movement, and it pumped up several body segments behind the head, tucking its head down at the same time. With eye spot markings on its flanks, a scaly pattern on the entire body, and by raising up the front part of the body, it really did look the part. I wasn’t fast enough to get a photo, but I did get some video of the recovered caterpillar continuing on its way afterwards.

Searching the internet later, I found several good images of the caterpillar mimicking a small snake. Perhaps the best of these is show below.


The caterpillar looking very much like a snake (credit iSpot)

The natural world is so amazing, and so full of surprises, but mimicry is quite a common feature in both plants and animals. The European white dead-nettle has leaves that cannot sting but match the appearance of the unrelated stinging nettle very closely. Some insects look like pieces of wood, or a leaf, or a patch of white lichen, or a bird dropping. Many slugs look very much like animal droppings of various kinds, and as they move so slowly only an alert predator is likely to notice them. Predators, too, use camouflage which is not truly mimicry, but helps them merge into dappled sunshine and shade. Fish are often dark on top and silvery underneath. Sometimes they are patterned and look like the gravel bed of a stream or river.

Amazing!

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Life together

Only living things can form a murmuration. Not only that, the individuals must all be alive with the same kind of life, don’t expect to see seagulls and starlings together in the same formation.

A murmuration of starlings

This morning, swilling out the cafetiere, watching the dark coffee grounds fan out and spiral down the drain, a word popped into my mind – ‘murmuration’. This word is used for a flock of birds flying together, swirling hither and thither, flying together as one yet moving independently and in smaller groups within that one flock. Starlings are particularly known for this behaviour as they go to roost in the evening light, and the dark specks of coffee reminded me of a murmuration of these birds.

Murmuration of starlings

But looking at those coffee grounds made it very clear to me that only living things can form a murmuration. Not only that, the individuals must all be alive with the same kind of life, don’t expect to see seagulls and starlings together in the same formation. The living entities must also be in a fluid environment (air or water, large shoals of fish can exhibit the same phenomenon). And they must be aware of one another and able to respond rapidly to one another’s movements.

Take a look at this video of a starling murmuration. It’s stunning!

So it should be with the church. A formation of individuals all alive with the same life, the life of Christ, all filled with his Spirit. Church should be a fluid environment, the individuals free to move in every dimension, yet always aware of one another and responding to one another.

When the church flows like a murmuration, individually alive with Christ, individually free to move yet mutually aware, responding to one another’s presence and movement, unconstrained except in obedience to Christ, then, my friends, we will see her transcendent glory revealed and the whole world will gasp. People will say, ‘Oh wow, how can this collection of individuals flow together with such transcendent beauty and grace?’

If not, we are little better than coffee grounds swirling into the drain. Not alive at all, merely acted on by random currents as gravity draws us ever downwards. Paul expressed this when he wrote to the church in Ephesus,

We must no longer be children, tossed to and fro and blown about by every wind of doctrine, by people’s trickery, by their craftiness in deceitful scheming. But speaking the truth in love, we must grow up in every way into him who is the head, into Christ, from whom the whole body, joined and knit together by every ligament with which it is equipped, as each part is working properly, promotes the body’s growth in building itself up in love.