I am aware of biological constraints to our size, such as the issues presented by Vsauce in this video.

However, letting the biological factors aside, what is the perfect size for a technologically advanced species? There are some benefits to being small: materials are stronger, more abundant and the world is a bigger place. However, they might be harder to procure and process. Also, scientific exploration might be an issue.

Note that the question refers to the size of one species on Earth, considering that everything remains the same (e.g. the size of trees).

Later edit: The main point of the question is about the technology itself and the manufacturing process (e.g. if we had been 1cm tall, could we manufacture laptops of appropriate size?) and what can we and cannot build anymore?

  • $\begingroup$ Hi Paul92. As we say in the tag wiki, avoid using only science-based/hard-science/reality-check to tag a question. I added creature-design because I believe that is appropriate to describe what you are asking about. Feel free to edit further should you come across other tags that you feel categorize your question better. $\endgroup$ – a CVn Dec 25 '15 at 14:09

Given the rather small sample size we have on Earth, Human beings seem to be the "ideal" size for intelligent and technological creatures.

Dolphins and other Cetacea are probably very intelligent, but live in an aquatic environment (meaning they cannot discover and use fire), and have no hands or other manipulating appendages. A marine creature of similar size and composition might be able to become both technological and intelligent if it had hands, and would almost certainly do so if it was also amphibious to the extent it could work for long times on land.

Other creatures on Earth do seem intelligent, and some have some ability to manipulate the environment around them, including elephants, some birds like crows. squid and octopi and of course our own cousins, the chimpanzees. The primary issue that seems to hold them back (besides a terrifying competitive species Homo Sapiens invading every ecological niche) seems to be the "brain-body mass" ratio. In essence, the size of their brains, while large compared to other creatures of their order and even in absolute terms, is still small in proportion to their bodies. Since Homo Sapiens is the only example of a fully developed technological species that we know of, that suggests the modern human brain size sets the lower boundary of how large a brain needs to be in order to be able to process abstract thought, manipulate objects and language and become fully technological.

So assuming a similar architecture of the brain, then a technological species existing on an Earth like planet will probably be similar in size to modern humans and have a brain proportionately sized to the body. I suspect that (with certain allowances) this ratio might even remain true for hive creatures, so long as the assembled "intelligent" hive achieves a similar brain-body mass ratio. If you are postulating a different brain architecture or a different sort of planet and biochemistry, then all bets are out the window.


Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

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    $\begingroup$ Regarding the aquatic animals component of your answer, there are good previous questions you can reference on underwater organisms potentially creating technology, forging tools, using geothermal vents as a heat source, etc. $\endgroup$ – Wingman4l7 Dec 25 '15 at 9:46
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    $\begingroup$ I'm not sure this answer meets the criteria for the hard-science tag. Please add some references to back up the claims made, in order for the answer to meet the hard-science criteria. $\endgroup$ – a CVn Dec 25 '15 at 14:10
  • $\begingroup$ Interesting point of view. I haven't thought about the brain size issue. However, the main point of the question was regarding the technological aspect: material resistance, minimum size of some components like engines, etc. $\endgroup$ – Paul92 Dec 28 '15 at 9:10
  • $\begingroup$ Once a species becomes technological, their developments begin to diverge from the scale and scope of their own size. Ancient Egyptians built the pyramids with tools no more sophisticated than copper chisels and wooden rollers, while today we build computer chips with features built on a scale of nanometers. Other creatures which use tools only scale to what fits in an hand, trunk or beak. $\endgroup$ – Thucydides Dec 28 '15 at 11:05

I'm assuming an alternative Earth in the following. Same physics, climates, DNA based life, fish as common ancestor to all higher land based life. No centaurs or superintelligent insect colonies.

Maximum size is quite easy. Something like a gorilla. Much larger and falling over becomes a hazard to life. But an elephant doesn't have hands and can't evolve into a centauroid because it's body plan was set by its fish ancestor. I don't think a trunk is a sufficient substitute for hands for developing technology.

Now the interesting direction. Smaller. The basic physics is that surface area goes as length squared but volume as length cubed.

A creature 10% the weight of H.Sap. couldn't support a human sized brain. Is that necessary? I think not. There have been people with anomalously small brains which were discovered at post mortem of a "normal" person. And there's Alex the parrot who approached chimp intelligence on a walnut sized brain. So I'd deduce that a brain one tenth human weight might evolve to support human equivalent intelligence. One hundredth, I'd doubt. Not least because a third or more of our brain is dedicated to vision processing.

A half-scale human has one eighth of the brain volume. Such a biped would average around a meter tall. I've fudged upwards a bit because it would not need to be proportionally as thick set as a human. Smaller limbs can be more slender and a smaller body falls less hard.

Now given the necessary intellect and hands could it access technology? Consider some key developments.

Coming down out of the trees ( only environment that encourages evolution of hands?) Proto-humans could stand to see above the prairie. Is three feet high sufficient? There's no obvious route to using fire if you keep living in trees. OTOH meerkats exist.

Fire. Making fire by friction is not easy. The creature has to dump sufficient muscular energy into a dry stick in a short time window. Like most kids I have tried and failed. Could any creature with one tenth human average arm muscle mass succeed? Perhaps, especially if it had theropod dinosaur ancestry rather than mammalian. Birds are from that branch of the tree of life and can support a higher metabolic rate. Otherwise are natural fire sources sufficient to attain technology?

Weapons. A tribe of humans with spears can defeat any predator often enough that the predator learns to leave humans alone or becomes extinct. Could a one-tenth human-mass creature become the top predator? Also could they develop bows and arrows? A scaled down arrow rapidly becomes non lethal.

Agriculture. Could these creatures domesticate oxen and horses? If not then ploughing becomes problematic as does keeping large wild herbivores away from the crops. Also the wheel works better for ox-carts than llama-carts or human-carts. The Incas didn't get to the wheel.

I hope this is food for thought. Technology would clearly be harder to attain for a creature with human intellect but one tenth our body mass. It feels like a lower limit even if you bless it with dinosaur genes.

  • $\begingroup$ a hint on the oxen: 1/8 of the body weight should mean 1/8 of food requirements i think. So a smaller animal dragging a smaller plough to till 1/8th of the land area in the same amount of time should work just fine, or am i missing something? $\endgroup$ – Burki Feb 2 '17 at 10:49

TLDR: Smaller is more ideal

Well, Homo floresiensis were tiny, measuring only about 3 feet in height. They were not midgets or dwarfs, simply a much smaller version of Homo sapiens. In an alternate universe they very well have been the norm for our planet, but I think much of our size has to do with competing against predatory animals, which tend to be larger than their prey. If you had a non-meat eating race with only limited exposure to predators it could be smaller since it doesn't need to out-chase or fight for food, or defend itself.

Coincidentally, the Spartans were the fiercest and most efficient fighters of their age, and Greeks tend to be much smaller than Germans or Nordic based people. I mention this because weapons are what really blossomed technology through the ages. Being small has a lot of advantages as you need fewer resources to survive (less food, less material for clothing, smaller structures for housing, etc.). This means those same resources can be spread out over a greater number of people, which means more minds working to create new discoveries.

In summary, the smaller you are the more densely you can live, the less food you need, the lower the impact you have on the world... there's also a study that shows that shorter people live longer than taller people. This leads me to surmise that smaller is in many ways better, but due to circumstances of who won which war, population growth, etc., we are on the larger size these days. Our size has not affected our intelligence, and there's no current evidence that we would have had more/fewer technological advances had we evolved smaller.

  • $\begingroup$ Interesting insight on why are we this size. However, the question asks about the smallest size while being able to be technologically advanced. Could 1mm humans build smartphones, melt steel, cut trees? $\endgroup$ – Paul92 Feb 2 '17 at 8:16
  • $\begingroup$ True, I seem to have gotten into a tangent last night. This did, however, prompt a question of my own based on a parrot sized brain's capacity. $\endgroup$ – mkinson Feb 2 '17 at 10:56
  • $\begingroup$ worldbuilding.stackexchange.com/questions/69918/… $\endgroup$ – mkinson Feb 2 '17 at 16:06
  • $\begingroup$ My TLDR response still stands. Smaller is better, and if there were atomic sized organisms capable of advanced thought they'd rule the universe simply because they'd be the most capable of producing in innumerable quantities with the smallest impact on resources per individual. We've proven we can create gears and other complicated mechanisms in microscopic proportion, just think of what could be accomplished when you can manipulate molecules in proportion to yourself. $\endgroup$ – mkinson Feb 2 '17 at 16:10
  • $\begingroup$ We've proven that we can build microscopic gears with macroscopic tools and macroscopic material gathering/purification. There is no question that nanotechnology exists, but can it be designed built by small humans? There is also the issue of material availability/the amount of travelling requied. $\endgroup$ – Paul92 Feb 2 '17 at 16:14

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