5 unsolved scientific mysteries

Alan Martin March 24, 2016

There’s an awful lot that science has solved, but not everything has a clear answer… yet. Here are five problems where we have theory and conjecture, but nothing solid.

Why do zebras have stripes?

I know what you’re thinking: “Obviously zebras have stripes for camouflage purposes”. That was the majority of scientists’ assumption as well, but it doesn’t seem to be true: the only distance at which stripes would provide any confusion for predators would come after they could already smell the zebra, researchers found this year.

So what are the other possibilities? One group of researchers reckon it’s because insects prefer to feast on animals with a solid colour, while another suggests it’s down to temperature control.

Not the most pressing scientific dilemma out there, of course, but a puzzle all the same.

Why does this water flea have more genomes than humans?

The number of genomes seems to bear little relationship to the complexity of the organism. Humans have 20,000-25,000 genomes. A tomato, on the other hand has 30,000.

But the winner in terms of complexity is the Daphnia pulex, a species of water flea, with a whopping 31,000. This is known as the C-value paradox, and it’s still not entirely clear why it happens. In the case of the water flea, scientists speculated at the time of this discovery that “since the majority of duplicated and unknown genes are sensitive to environmental conditions, their accumulation in the genome could account for Daphnia‘s flexible responses to environmental change”.

But it’s still just speculation.

Where are all the aliens?

An extremely conservative estimate suggests there could be upwards of 7,500,000,000,000,000 planets that are capable of harbouring life, and many of those with the right conditions to sustain it for much longer than us.

So why have you never met an alien?

That’s the Fermi Paradox in a chilling nutshell. There are plenty of plausible explanations for it, and some of those suggest it’s because all civilisation destroys itself before it gets advanced enough to enjoy a jaunt beyond its home galaxy. Cheery.

Why don’t whales get more cancer than us?

Cancer is the uncontrolled growth of cells. If you have more cells, you should have more chance of developing cancer over time, so why are cancer rates in blue whales – the biggest mammal on the planet, with a lifespan of up to 200 years – not significantly higher than humans? This is Peto’s Paradox.

To be clear, we don’t know for sure how many blue whales get cancer, but that’s not really the point: if blue whales were to match the human model, then there wouldn’t be any blue whales left. There are, so why don’t they get cancer at the same rate as humans? And for that matter, why don’t mice with far fewer cells get around the same rate as us? We don’t know.

Why does the placebo effect work?

If you’re sick, and you expect a pill to help the symptoms, it often does. That’s true whether it contains real medication or just sugar. What’s more, we know that, taken alongside genuine medication, placebos can boost the effect of the drugs. Why? We still don’t really know.

Some people are more susceptible to placebos than others, but to date we haven’t found an effective way of accurately identifying them. That’s a real pain, because our clinical trials would be far more effective if we could, as we’d be able to ensure only those immune to the placebo effect were tested.

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Images: Frank Wouters, Jason James Yasuo Kida, Olli Henze, Gregory Smith and Kev Shine used under Creative Commons