Thursday, 30 July 2015

Uprooting the Tree of Life

Yesterday I wrote a post about a cool new transition fossil. When writing it I was more than once tempted to make some kind of reference to the Tree of Life, but I resisted. Why? Put simply: because it would be wrong. There was a time when everyone, even people who were totally on board with evolution by natural selection, was under the impression that the species we see wriggling around today could be traced neatly back, branch by branch, to the ancestor that is common to all life and that those species that looked physically similar did so because they shared a branch on the tree. In the metaphor today's animals are represented by the fresh new shoots and buds on the mighty oak of life; each bud forms a neat ladder ever back to the base of the trunk that started everything, but this picture can lead to many misconceptions about evolution. A more modern understanding of the theory and the evidence we now have paints a different picture. The Tree of Life is dead, say hello to the Shrubbery of Life!

The traditional, misleading view of the Tree of Life
Actually, people generally say the Bush of Life but I saw a chance to use the word shrubbery and I ran with it. Instead of thinking of a perfect, archetypal tree that a 6 year old might draw, think of a tangled mess of thorns full of jagged twigs, thick and choking, jutting this way and that such that you can barely tell where one branch begins and another ends. This is the far better analogy. It allows for the possibility of animals arriving at the same physical niche via a variety of evolutionary paths. It also rules out the idea that as life evolves it moves ever upwards in an increasingly complicated and intricate manner, this isn't the case. Some species 'devolve', or lose features that they had previously evolved; some, like coelacanths or nautili, remain unchanged for millions of years.

Worry not, if you have a poster on your child's bedroom wall like the one on the right I'm not about to tear it down and set fire to it. But the next time you have a chat about it, as you undoubtedly do, use it as an opportunity to highlight that the reality is actually a lot more nuanced and complicated than we often like to think, just like every other single topic worth having a chat about.

Wednesday, 29 July 2015

I Love Transition Fossils

One of the many stupid arguments put forward by people trying to dispute the theory of evolution by natural selection is: if evolution is true then there should be fossils of missing links, if birds evolved from dinosaurs then show me a fossil that is half bird and half dinosaur. Now, asides from the fact that this shows a gross misunderstanding of the theory there are actually a great deal of 'missing links' out there; they're called transition fossils and there is now a quite beautiful catalogue of them. We have transition fossils for pretty much every major order of animals out there, the only exception I can think of is bats, we don't yet have a decent fossil record of their evolution - it's only a matter of time, though.

We have ambulocetus, a wonderful cetacean (whale and dolphin) precursor that could swim well and walk around on land too; we have tiktaalik, a transition fossil of a fish that had 4 primitive legs and was well on its way to being an amphibian; and we have the legendary archaeopteryx, which is quite literally half bird half dinosaur. The fossil record, by its very nature, will never be 100% complete, but it is now well stocked with a plethora of transition fossils all of which add support to the now invincible edifice that is evolution by natural selection, and, I'm pleased to say we can now welcome another strut to the structure.

tetrapodophis snake, transition fossil, evolution, science
Image used with permission

An article in Nature has given details of an awesome new transition fossil; it is quite clearly a snake but equally clearly it has four little legs. The legs would not have allowed it to walk, they're too small and it's body is too long, but they may have allowed it to grab prey a little easier or get a better grip when mating hence its name: Tetrapodophis amplectus which translates as four-legged hugging snake.

For a long time it was uncertain if snakes had evolved from land animals or aquatic animals. If the latter then we would expect to see a transition fossil with a tail adapted for swimming and vestigial fins; if the former then we would expect, well, we would expect exactly what this fossil shows. Another little gap in our knowledge has been filled in, leaving one less place for evolution deniers to hide.

Tuesday, 28 July 2015

A-Hazing New Pluto Picture

Exciting news Plutophiles! Last Friday NASA had another Pluto press conference and in it they released the latest images from New Horizons, the most amazing of which was this beauty below.

Pluto, haze, NASA, astronomy, science

This is an image taken by the probe after it has sped past Pluto. It is looking back at the night side of the world 7hrs after closest approach. The halo around the edge is the hazy atmosphere backlit by the sun. It was only recently that we even became sure that Pluto had an atmosphere; the data here shows that it does indeed have one, that it extends about 80 miles above the surface and that it is comprised mainly of nitrogen. But the haze is actually the interesting bit. The haze is made up of complex hydrocarbons, like ethylene and acetylene, which are created when ultraviolet light from the sun interacts with methane gas in the atmosphere. The UV light in turn changes the hydrocarbons into tholins, these fall back to the surface and are what gives the dwarf planet its now distinctive dark patches.

Pluto has once again, however, thrown up a mystery. These hazes are created by the hydrocarbons condensing into little ice crystals, but it was thought that Pluto would be too warm for this to happen at a height of above 20 miles or so; yet we're seeing haze as high as 80 miles and we have absolutely no idea how. Some new ideas are needed to come up with a satisfactory explanation for this, but that's a good thing; if the answer to your question doesn't throw up at least a couple of new questions then you're not doing it right and that, Science Fans, is one of the exciting things about the frontiers of science.

Monday, 27 July 2015

New Earth-like Planet Discovered

Last Thursday NASA called a press conference. It was a bit out of the blue but we were given a heads up that it had to do with Kepler so everyone knew they would be announcing a newly discovered earth-like planet; and so it came to be. Kepler, of course, was the planet hunting satellite named after Johannes Kepler the German mathematician and astronomer. Kepler worked using the transit method; it would stare at thousands of suns and look for tiny dips in the levels of brightness, this could indicate that a planet had passed in front of, or transited, the star and temporarily blocked some of its light. If a dip was found to have a regular pattern then there was a good chance it was a planet. Using this method Kepler has found many thousands of candidate planets, 1879 of which have been confirmed at time of writing.

Thursday's announcement of planet Kepler 452b was a little different as they claimed to have found the exoplanet most like our own. The planet is a rocky one about 60% larger in size than the earth but about 5 times more massive, so it's likely to be very volcanic with quite a dense atmosphere. Its sun is 50% or so larger than our own and a billion years older so it's likely to throw out a lot more heat than we're used to experiencing. This combination could actually mean that conditions on the planet are too harsh for life to exist, certainly complex life anyhoo.

Before this announcement the most earth-like planet discovered to date was Kepler 186f. This is a rocky world no more than 10% larger than us orbiting a red dwarf star. Even at midday this world would only be about as light as sunset here on earth, despite this I think 186f actually remains the most earth-like planet we have yet discovered. Sorry Kepler 452b.

Below you can see the four most earth-like planets and their stars discovered by Kepler so far with the earth for comparison.

NASA, science, astronomy, Kepler, planets, transit method
Image courtesy of NASA

Friday, 24 July 2015

Our Saviour: Bacteriophages

Parkinson's Disease (PD). Alzheimer's Disease. Creutzfeldt-Jakob Disease (CJD). Transthyretin amyloidosis (TTR). These are diseases that are increasingly blighting our society. Almost everyone will have now heard of the first two as the misery of dementia slowly ebbs further into the public consciousness. CJD is the infamous mad cow disease that had the world panicking in the 1990s. As chance would have it I happened to be doing some work just today during my day job on TTR, a disease that can ravage the heart and liver.

Although these diseases can present in a variety of different ways they all have something in common, something that may play to our advantage. They are all caused by the misfolding of proteins. Yep, as simple as that. The abject horror of losing your mind to Alzheimer's is the result of a protein folding up slightly wrongly and producing a little kink that renders it insoluble in your cells. These misshapen chains of amino acids aggregate together into plaques that become toxic and kill your brain cells; we currently have no way of removing them. In PD we call them Lewy bodies, in CJD they're prions but the subtle differences between them all may be rendered irrelevant by a new drug that specifically targets the kink in the protein that unites them all.

Researchers at NeuroPhage Pharmaceuticals have released data from animal trials that shows their drug is capable of breaking up the plaques and subsequently improving their cognitive function. They have applied for a licence to do human trials and hope to start small scale trials in PD patients next year. The drug is derived from M13 bacteriophages, a very common organism in biomedical research. Bacteriophages are vanishingly small viruses that infect bacteria (a fact that makes them one of our best bets for the next generation of antibiotics), many thousands of them can fit inside a single bacterium. The drug comprises of two parts. The first is a compound from the M13 phage that can recognise and bind to the kink in the deformed proteins. The second is a human antibody that the first part is bound to. The antibody signals to the body's immune system that the plaque needs to be sequestered away and destroyed.

This compound is still a very, very long way away from being a useable drug, probably five years minimum, and there's probably an even chance that it won't come to anything; but it does show promise.