Just how scientifically possible are Gremlins?: Part 2

28 May

And so we (finally) come to Part 2 of this series! If you haven’t read Part 1, I suggest you follow this link and get up to speed otherwise this might seem a tad strange! In this part, we’ll look into the second rule that the ‘Gremlins’ films set out for caring for a Mogwai (or Gremlin if you were unfortunate enough not to have read Rule 3 before giving your Mogwai a bath!). We’ll also be asking whether these creatures’ mischievous/dangerous behaviour is like anything seen in nature. We’ll start with a recap of the rule. Enjoy!

Rule 2. Never expose them to bright light.
Bright light scares Mogwai and Gremlins alike, whilst sunlight kills them.

The first question to ask is whether any species in nature is actually scared of light. The short answer is… sort of…but not really! We’ve all seen moths being drawn towards lights at night – this behaviour is called ‘positive phototaxis’. If there’s such a thing as ‘positive phototaxis’, then ‘negative phototaxis’ must exist too, I hear you cry! And indeed it does – many organisms can be seen to actively avoid exposure to light. Many species of cockroach, for example, will avoid lights and well-lit areas; and a tiny roundworm called Caenorhabditis elegans (catchy, I know) can be made to change direction by shining light on its ‘head’.

Now, none of these species are scared of light as such – their behaviour is simply instinctive (or ‘innate’) and designed to help them survive. Cockroaches are far more visible to many predators when exposed to light, so they instinctively avoid it. The roundworm, meanwhile, lives in soil and uses the detection of sunlight to determine in which direction it should move in order to stay buried in the soil where it feeds on bacteria. So, these creatures aren’t scared of the light itself; but they know to avoid it in order to improve survival. This tends to be the case in all ‘negatively phototactic’ species.

It could, of course, be argued that Gremlins aren’t scared of light in the way we think and that they just instinctively know to avoid it because sunlight kills them. If they have evolved to avoid all sources of bright light then they would increase their chance of survival. On balance, I think I’m going to say that this part is quite realistic and scientifically possible!

The next question is whether anything in nature can be killed by sunlight. Whilst no animals are directly killed by light, they can be killed by the long-lasting effects it has upon their bodies. We are, of course, talking about skin cancer caused by the ultraviolet light emitted by the sun. This radiation is split into 3 categories – UV-A, UV-B and UV-C – depending on the wavelength of the light. UV-A has the closest wavelength to that of visible light and, since visible light does no damage to animals’ skins, UV-A does relatively little. Meanwhile, UV-C is usually absorbed by the Earth’s atmosphere, so its effects on animals are rarely seen.

The light spectrum, showing the wavelengths of the 3 different types of UV light (Photo Credit: Ken Costello at

The light spectrum, showing the wavelengths of the 3 different types of UV light (Photo Credit: Ken Costello at

UV-B is the most common cause of skin cancer. Due to its wavelength, UV-B is absorbed by DNA. In my first post I talked about how DNA is made up of combinations of molecules called A, T, G and C. Well, UV-B radiation causes Ts to bind to one another when they shouldn’t. Now, small amounts of this DNA damage occur frequently with sun exposure, but it is rarely a problem as healthy cells are capable of repairing damage to their DNA. It is when the level of damage is too great or DNA repair mechanisms break down that mutations build up, increasing the possibility of a mutation leading to the development of skin cancer. So, whilst not exactly a direct cause of pain and death, sunlight is involved in killing many animals. The effects are not quite as severe as those seen when Gremlins are exposed to sunlight though, so I must admit that skin melting under sunlight exposure is quite unrealistic!

I should say, as a caveat, that ultraviolet light is capable of killing bacteria and viruses pretty much instantly (even faster than it can kill a Gremlin). However, given how long this post is already going to be, and given that these microorganisms cannot really be compared to Gremlins, I’d best save that one for another time…

Ultraviolet (UV) photons harm the DNA molecule...

UV light breaks the bonds that hold together DNA double helices. Most commonly, it breaks bonds involving thymine molecules, which then bind to one another instead. In this malformed state, the DNA cannot function. (Photo credit: Wikipedia)

What I’d like to go over next is why Mogwai and Gremlins are so aggressive and mischievous. As with many of the characteristics displayed in the film, this can be seen in many species in nature, albeit in a muted, less entertaining way.

In the films, the Gremlins have essentially been dropped into an unknown environment. You could view their anarchic behaviour as attempts to adjust to, and assert their place as a dominant species in, a new food chain. If seen this way, Gremlins could be said to be an ‘invasive species’. There are many examples of such organisms in nature (although obviously none of them take over cinemas or attack New York hotdog stands!). Often they are artificially introduced into an environment by human activity, either intentionally or accidentally.

A high-profile example of an intentional introduction is the Cane Toad, which has been a blight upon Australia ever since being taken there, from its native Hawaii, in 1935. Originally envisaged as a way of killing off Cane Beetles, which were destroying sugar cane crops, the toads acclimatised far more successfully, and with more severe consequences, than anyone imagined.

The massive and destructive Cane Toad ranks as...

The oh-so-beautiful Cane Toad (Photo credit: Wikipedia)

Since their introduction to their new environment, their numbers have swollen from a few thousand to over 200 million. They have spread diseases, outcompeted native species, poisoned almost anything that tried to eat them and generally disrupted the finely balanced ecosystem through their aggressive behaviour. And to add insult to injury, they’re not even effective at killing Cane Beetles!

So, clearly there can be serious consequences to mankind’s manipulation of nature. People are learning that we cannot predict every change that will be caused by introducing a foreign species into an ecosystem. Unfortunately, sometimes we cause ecological disasters without even intending to alter an ecosystem. Invasive species are often destructive and cause a great deal of harm to native species. In this respect, Gremlins very much fit the bill. As for the mischievousness… well, they aren’t the only naughty animals out there!

(Video credit: Hassanane’s YouTube channel)

That brings us to the end of Part 2 of this post. I hope you’ve enjoyed it, as Part 3’s coming whether you want it or not! Before that, though, I’ll be bringing you the first post from a couple of fellow bloggers, as promised earlier in the week. Keep an eye out for that one – these guys are good!


Posted by on May 28, 2013 in Biology, Silly Science


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5 responses to “Just how scientifically possible are Gremlins?: Part 2

  1. Sazzy

    June 7, 2013 at 10:27 AM

    How did I miss this? Woo more gremlins, gremlins vs chimps would be something I would like to see. Thank you for interesting post, I shall now enlighten work about sun and dna as it is sunny and it’s Friday so distraction is even easier than normal 😀

    • Science Gremlin

      June 7, 2013 at 2:25 PM

      Haha no problem – I’ll be doing the final part in the next week or so 🙂 And gremlins vs chimps? As in the differences between them or a fight to the death?!

      • Sazzy

        June 18, 2013 at 10:41 PM

        Why did my email not notify me of this reply…despite the fact I told it too? >_<;

        A fight, but the more I think about it, there's a good chance they would combine forces and just become a troop of mischief makers and cause trouble where ever they go.

        Alternately could do it top trumps style;
        Resistance to sunlight – Chimps win
        Playing cards – Gremlins win
        Using kitchen appliances – more research into chimps and kitchens needed.

        Why is this not a Top Trumps game? Pretty much everything else ever is. I may have to make some cards haha 🙂

      • Science Gremlin

        June 23, 2013 at 2:51 PM

        Internet fail! He says, posting 5 days late… 😉
        Hmm yeah an army of Gremlins and Chimps might be unstoppable! Especially if they manage to mate and we’re faced with Grimps and Chemlins instead!
        Haha I love the idea of it being a Top Trumps game – as soon as you make those cards let me know and I’ll be there to play!


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