Okay, I just asked a question, in which mother nature transformed all animals (or brain containing living beings, if that fits better for you) into a being twice as big in order for them to kill of humankind, recovering the ecosystem.

Well, with twice the heigth, length and width, it's actually eight times the size ($2^3$).

The question was, if humankind could remain as the dominant species and the answers made it clear: Yes, easily.

But it got me thinking. Would the result be the same, if all animals would have turned twice as big at the year 0?

The rules are the same:

  • This transformation happened worldwide at the same time and only took about a minute.
  • The physical abilities (strength, speed etc.) scale accordingly to the size and the animals are able to handle the gained mass just as good as their reallife counterparts.
  • Mother Nature DO provide the earth with enough food to feed the bigger animals. After all, she wants to keep her children alive, killing only humankind. Well, carnivore don't need changes, as their prey scale accordingly. Let's just say the vegetable food grows faster, there is more of it or it provides more of whatever keeps the animals alive. (Doesn't really matter, the question is about the fight between humankind and animals)
  • The earth was EXACTLY ours until the year 0.

With all that: Would humankind still be able to become the dominant species in the year 2000 (or earlier), or wouldn't they be able to handle the changes?

  • $\begingroup$ Seeing how primitive humans already hunted and took down many mega fauna I imagine it would only be a set back for a time before we found a way to take advantage of the new massive influx of food. But that's just an educated guess, I don't have enough evidence for a full answer. Not to mention very few animals would be hunting humans trying to wipe them out so you'd have to change their behavior to want to attack more. $\endgroup$
    – Virusbomb
    Commented Jun 1, 2017 at 21:44
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    $\begingroup$ Do the animals' psychology change? Do they suddenly rise up against humans or carry on living their own lives? $\endgroup$ Commented Jun 1, 2017 at 21:48
  • $\begingroup$ Better read "On being the right size" here...irl.cs.ucla.edu/papers/right-size.html $\endgroup$
    – DJohnM
    Commented Jun 1, 2017 at 21:58
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    $\begingroup$ Technically 'year 0' does not exist in the Anno Domini system. Use 1 BC or 1 AD. source: en.wikipedia.org/wiki/Year_zero $\endgroup$ Commented Jun 1, 2017 at 22:41
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    $\begingroup$ Animals are no match against humans, no matter the size, and haven't been a match for us for the last 200,000 years at least. If you want Gaia to kill us humans, try viruses and bacteria instead. $\endgroup$
    – Rekesoft
    Commented Jun 2, 2017 at 7:34

6 Answers 6


Unless the animals are magically guided to specifically attack human beings, no way.

Specifically, humans already did this once, about 12 thousand years ago. The giant ground sloths, giant rodents, regular lions and tigers on the American continent were systematically wiped out for practical or culinary reasons in the centuries following human arrival.

Humans needed flint, sticks, fire, and language. They still have all these things in the year 0, but now they also have armies, written language, boats, and metals.

If you would like a specific example: The polar bear hunters of Zhokov island. 397 polar bear skulls, hunted with bone and stone tools.

  • $\begingroup$ Australian Aborigines did the same thing as small hunter gatherer stone age groups and pygmies hunted elephants. $\endgroup$
    – Kilisi
    Commented Jun 1, 2017 at 23:03
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    $\begingroup$ The Australian case is actually a better example. In North America an extra terrestrial impact (probably a comet fragment) also played an important part. Also, the Australians, unlike early Native Americans, didn't even have domesticated dogs to help them and were in harsher conditions. $\endgroup$
    – ohwilleke
    Commented Jun 2, 2017 at 5:14
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    $\begingroup$ I'd add that people have been killing the largest animals, whales, with primitive tools (sailing ships and man-powered harpoons) for a long time, and those are pretty intelligent creatures. 8 times more brain does not make an animal 8 times more intelligent. Microbes may wipe out year zero man; but any brained animal that wants to wipe us out better have overwhelming numbers everywhere we exist, or they better be able to plan at least one move further into the future than us; as long as we can plan one move ahead of them, we win. Make them big: I still know where their carotid is. $\endgroup$
    – Amadeus
    Commented Jun 2, 2017 at 13:28

Possibly Yes.



I'll begin with a rough list of various technological achievements by 1 AD:

  1. The Great Wall of China had already been constructed in whole (by ~100BCE) and part (by ~700 BCE).
  2. The Romans had constructed aqueducts (312 BCE) and roads (~300BCE).
  3. The Romans had begun using hydraulic mining in NW Spain by 25BCE.
  4. The Romans and Chinese had 200 and 300 years of respective experience forging steel.
  5. The Chinese had 500 years of crossbows.
  6. Sun Tzu's Art of War was written by 500BCE. (though not a technology it was an impressive and lasting achievement nonetheless)

Note: China wouldn't fully develop gunpowder until Wujing Zongyao was written in 1040-1044 ADE; however, Saltpeter was known to the Chinese by the mid-1st century AD


By well over 1000 BCE Homo Sapiens had already hunted down animals significantly larger than them (Woolly Mammoths, Elephants). As @Resonating noted, we also wiped out large animals on the American Continents. Fastforward to 1ADE and 3 major empires are present:

  1. Roman Empire under Augustus
  2. Chinese Han Dynasty
  3. Parthians

Of them I'll ignore the Parthians since I'm unfamiliar with their history.


BY 1 ADE the Roman Empire had been ruled by Augustus for 28 years. Following "The Transformation", city dwellers would panic over the size of vermin and rural citizens would panic over the size of their cattle or wild animals. The cities would calm rather quickly given the presence of Praetorian Guard, police, and fire fighting established by Augustus and the Roman Legionnaires of course (who happens to include rural farmers in their ranks). Given the large presence of weapons among the populace, I expect they'd make short work of any animals that happens upon them. Deaths by mauling or animal attacks would surely increase; but, this would motivate a systematic response from the Senate and Emperor.

Given their technological prowess, I expect the Romans would construct walls to keep out larger animals. Unlike the Germanic tribes, the Romans would benefit from light sources, horses, roads, and steel/iron weapons. As such, the Germanic tribes would never become a threat to the Romans. Furthermore, given the different chain of events, it's debatable whether Augustus would die when he did (14 AD), especially if Livia did poison him. Considering the Roman Empire's existing domestication and distribution channels the Roman food supply would increase eightfold from meat sources and massively from agriculture (since agriculture would grow to compensate for the animal's increased diet). Furthermore, it's not a stretch to consider how quickly they'd attempt to tame said animals and use them for work or transportation. One of Rome's biggest technological issues was energy sources. With 'The Transformation', every animal they put to work would output 2-8x more energy. How far could a horse 2x taller and longer travel? Imagine how that would affect the Cursus Publicas (also implemented by Augustus)? How would this affect the ability to transport the materials needed to construct walls and aqueducts? This would be a very different Roman Empire without much of the limits that crippled it by 1000 AD.

What is questionable though is the status of their outlying regions (Egypt, Anatolia, Phoenicia, Spain, France). Here I won't speculate (for the moment).


Unlike the Romans, the Chinese are a different beast. By 1 AD they'd mastered warfare and have strongly unified. With the onset of "The Transformation", they'd have the capacity for a rapid response. Since they were quite familiar with East Asia, they'd successfully wage a land war against the animals. I say this because they have strategy, steel weapons, and most importantly: crossbows. Where the Romans have numbers & organization, the Chinese armies would excel in the use of Sun Tzu's stratagems and the skillful application of weapons. Given the knowledge of Salt Peter and China's history of technological advancements during 'war' (namely the warring states period), I have no doubt that they'd develop gunpowder centuries ahead of time.


Yes, Humanity would survive; but, it'd be a vastly different world likely dominated by Rome & China.

Further Questions

  1. What animals would pose an existential threat to mankind?
  2. When would the scientific revolution occur in this new world?
  • $\begingroup$ It should be "By 1 AD" or "By 1 BC". It went 2BC, 1BC, 1AD, 2AD etc. although they weren't called that at the time. By our current calendar system there was (has been?) no 0 AD. $\endgroup$
    – wizzwizz4
    Commented Jun 2, 2017 at 12:36

I'm going to be a contrarian on this one.

Hypothetically, if the point is to wipe out humans, would we even be capable of using animals for agricultural work? Without machinery, farming for large populations becomes difficult to sustain. While we could always hunt for meat, plowing is EXTREMELY energetically intensive, and there wouldn't be enough "wild food" to sustain human populations at 1 A.D.

Early hominids were grouped in small populations and fairly mobile in order to follow their food sources (excepting food rich environments like inhabited jungles). Additionally, EVERYONE was taught the skills to survive, and specialization was comparatively mild.

The sudden cessation of all agriculture would lead to mass die offs. Even assuming slave labor, farmers would have a hard time plowing and planting crops, since humans are weak in comparison to domesticated mammals. Basically all city dwellers would die, since they lack basic survival skills. Soldiers and the like might learn to hunt large game, but military tactics and formations used against large groups of humans don't translate well to individual animal quarries. Regardless, a population sated with meat would still suffer nutritional deficiencies. Your empires would fall without their bread baskets, and while small populations of subsistence farmers might remain, it's likely that genetic inbreeding would eventually lead to gradual extinction.

TL;DR: Early humans survived against megafauna due to small populations, high mobility, and lack of specialisation. By 1 A.D., our accumulation of technology means none of these factors hold. If we lose the capacity to engage in agriculture due to the larger farm animals "un-domesticating," then it is likely that humans will slowly go extinct.


Well honestly if even normal animals had been organized to attack humans(even without doubling size) then humans would already have been wipedout. So, if "mother nature" is trying to destroy humans in such a roundabout way(I mean it should be able to kill us all in a thousand different ways), then I can only assume that 'she' would still not be able to organize that when they are larger.

However even if the animals grew bigger, stronger and then became more agressive towards humans. Without the inteligence or instruction to wipe out all humans, humans would more than likely survive, adapt to the situation and then grow again; because necessity is the mother of invention and humans are like cockroaches.

Ofcoarse if a being intelligent enough to hunt all humans down is born and it has the abillities to back it up then the likely of humans being destroyed rises significantly. Also humans could just be unlucky.


Are animals that are 2x bigger actually more dangerous? (not really)

(Blatantly copying my answer to a similar question)

This analysis assumes that all the organs of the animals are scaled evenly in all directions.

There is something called the square cube law. There are many good things that grow with the square of the of the scal like muscle strength (which is proportional to the cross section area of the muscle) so 2x in each dimension is 4x strength.

There are many bad things that grow with the cube of size like weight which is proportional to the volume of the creature. So 2x in each dimension is 8x weight. Since the creature is caring 8x the weight it must consume 8x the calories to not starve. The required strength of lungs and heart which now must supply oxygen to 8x muscle, and push 8x the blood volume 2x higher.

Assuming that running speed is proportional to strength / weight we would expect large creatures to be twice as slow.

A larger creature has a harder time with stealth.

What does this mean

  • Some species would die out.

Some species would no longer fit in their ecological niches, bees would be to large to drink pollen from flowers monkeys could no longer climb trees water striders will no longer walk on the surface of the water. Some could not consume enough calories Cows eat most of the day to get enough calories, there is not time for them to eat 8x more. They would either have to switch to a more calorie dense food or starve.

  • The large animals would be very venerable to bows

The creatures are very large targets that are significantly slower than the ones we have today. They have 2x higher blood pressure so they will bleed out much faster if wounded. They are huge targets and will trouble sneaking up on anything. They must eat much more so they cannot afford to stalk or wait long they must attack.

  • They would be much more deadly at close range.

A giant lion would be capable of impressive destruction, but if a lion reaches you, you are dead anyway whether or not it is giant or normal.


Pretty sure this will be closed soon. So I'll try to help you. First, you really can't just double the sized of animals and have them move or even exist the same way. As you pointed out their volume goes up with the cube while their surface area only goes up with the square. This is a big deal for energy exchange. Also, why didn't the humans double in size? Anyway, none of that really matters. Humans rule because we can manipulate tools. We routinely bring down larger animals (and sometimes fall prey to them) with all of them the size they are now. We still win. I use the term 'win' loosely here, since I can't say for certain that our reign will be as long or as fruitful as those that preceded us.

Also, if you are going to write this into a world, you should really work on your grammar. I'm not intending to be cruel here, just pointing it out. Sorry.

  • $\begingroup$ Why the down vote? Was it the grammar comment? $\endgroup$
    – ozone
    Commented Jun 1, 2017 at 22:15
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    $\begingroup$ Not my downvote but I imagine it's because the first half of your answer was filled with stipulations that are already talked about in the question and second part of it isn't usefull. Then the final bit should have been added as a comment. $\endgroup$
    – Necessity
    Commented Jun 1, 2017 at 23:26

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