spaceSpace and Physics

Study Suggests Intelligent Aliens Will Probably Be The Size Of Bears

guest author image

Caroline Reid

Guest Author

49 Study Suggests Intelligent Aliens Will Probably Be The Size Of Bears
1970 ... bears in spaaaaaaace! by James Vaughan via Flickr CC BY-NC-SA 2.0

A speculative study on the possible nature of alien life was formulated by combining statistics with the unknown of space; whilst certainly intriguing, some may consider the conclusions a touch un-bear-lievable.

Fergus Simpson, a cosmologist at the University of Barcelona, used some creative Bayesian statistics in order to predict what physical traits alien life is likely to have. Even though this information is purely statistical and then speculative, it's a good starting point to get scientists thinking about how to model extraterrestrial life. 


Simpson began by estimating how many beings might make up an alien civilization and came to an average of 50 million or fewer individuals. This is quite a lot smaller than Earth where the human population is thought to be around 7 billion, but Simpson considers Earth to be on the high end of the population spectrum. He also thinks that most of alien life will come from a planet smaller than Earth.

To make an estimate like this, pretend the Earth is the universe and the countries are planets. It is much more likely that a random human will exist in China (1-in-5 chance) than New Zealand (1-in-1600 chance), for example. However, it is more likely that a random country will be one with a smaller population since there are many more Italy- and Spain-sized countries than Russia- and China-sized countries. 

Simpson also reckons that humans fall lower than the median weight predicted by his calculations. Quite a lot lower, actually, since the median comes out at 300 kilograms (661 pounds); humans average around 70 kilograms (154 pounds). For reference, Earth animals that weigh about 300 kilograms include bears, tigers, and dugongs. 

This analysis supports the idea that larger animals are less abundant since they gobble up more energy and resources; think of a blue whale compared to an ant. However, there have to be some fairly colossal aliens out there for 300 kilograms to be the average.


Should alien life forms be as large as a bear, it is unlikely that they will be intelligent by human definition. Therefore, we probably won't be expecting any visits from flying saucers anytime soon.

The unfortunate truth is that it will be impossible to determine the accuracy of Simpson's claims unless we actually find alien life—and not just from one planet but many. Even if we could contact alien life and it was intelligent enough to pop over, there's still the risk that these alien-bear beings wouldn't be friendly. The prospect of becoming slaves to an alien race is now even more terrifying with the idea that alien overlords could be the size of polar bears, rather than the skinny green men many envisage.

To read more about the statistical caveats and criticisms of this study, click here.

[Via arxiv and Live Science. Header image "1970... bears in spaaaaaaace!" by James Vaughan, via Flickr. CC BY-NC-SA 2.0]


spaceSpace and Physics
  • tag
  • extraterrestrial life,

  • bears,

  • aliens