Staying mobile was the secret to our evolutionary success

Human technology is advanced thanks to our socialising. By staying mobile and/or living in large groups we can learn from more people.


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Why aren’t you (probably) worried about being eaten by a lion tomorrow? Because of our technology. It’s the secret to human success. But what’s our secret? Why did we get such cool toys but chimps missed out? Many explanations have been proposed. Most have been disproven. Now, a new computer model may have found the right answer: being mobile.

Or rather, interacting with a lot of people. Being mobile, or living in a large group, are two routes to achieve this. The real secret is the “encounter rate”. How often you interact with others. Mobility and population density are two ways to increase your encounter rate. By balancing these variable, our ancestors created the perfect storm of invention.

Do lots of friends make you an evolutionary success?

There’s a lot of things that make our species unique. How many of these contribute to our technological prowess? Your first guess might be wrong. It’s tempting to put our brains at the centre of attention, but how that can’t explain the variation in human technology. Hunter-gatherers and farmers both have the same brain; yet only one of those groups developed guns, germs, and steel. And even then, not all farmers made such massive technological leaps.

The reason humans developed our advanced technology is clearly more nuanced than “we iz smart”.

Research on surviving hunter-gatherers identified a potential answer: population size. Computer models indicated that learning from someone is imperfect. You likely won’t be as capable as every teacher you’ve ever had. So, over time, a society’s knowledge-based will degrade. Unless there are enough super-smart people to take over for those teachers and compensate for the average loss of knowledge.

This idea of trying to “outrun the treadmill” seemed to find support in existing hunter-gatherers. Larger groups tended to have a more complex toolkit. The most notable example was the indigenous Tasmanians. They became isolated (thus effectively shrinking their population size) and promptly lost much of their toolkit. Including how to fish, which was one of their dietary staples before isolation.

Simple bone points, used to make clothes, stopped being manufactured by Tasmanians even though people on the mainland continued to create them

Simple bone points, used to make clothes, stopped being manufactured by Tasmanians even though people on the mainland continued to create them

I was wrong

Like many other people, I was fond of this explanation. It had both computer models in support and actual examples from the real world. However, I was wrong.

The computer models this idea was built on were fundamentally flawed. They assumed that learning essentially stopped after the teaching phase was over. As though nobody ever gained knowledge or refined skills after they left school. Obviously, that’s absurd. When this ability to refine knowledge after learning was taken into account, the relationship between group size and technology vanished.

But what about the Tasmanians? The computer models might be wrong, but there’s something going on there.

Perhaps, but whatever it is it’s unusual. Larger reviews of hunter-gatherers found that population size and technology generally don’t correlate. My favourite example of this comes not from modern groups, but prehistoric ones. Some researchers investigated genetic evidence of population size in our ancestors. This was then correlated with the archaeological evidence of when our fancy technology developed. The two do not line up.

Population size inferred from different genetic sources (the different coloured lines) versus when "modern" technology appeared

Population size inferred from different genetic sources (the different coloured lines) versus when “modern” technology appeared

Staying mobile is the real trick

So, it’s clear that being part of a large social group isn’t the reason we have such fancy technology. Which raises the question: what was unique about us after all? A new battery of computer simulations has revealed the answer. It’s not about how many friends you have, it’s about how often you all hang out.

Obviously, the key to human success is learning. We can pass on knowledge to one another. Any great new invention isn’t lost when its creator dies. It can be passed on. And that gives other inventors a chance to improve it. This is known as the ratchet effect. It essentially explains why humans have such great tools. And why our closest relatives likely won’t ever get them.

We now know it’s not how many people you meet with which determines the spread of technology. But clearly, technology has to be linked to our social lives somehow. Some of the prior research on group size and technology found that group migrations could have a similar effect. You met a greater number of people if you were mobile. This allowed for a greater transfer of skills. The benefits of being mobile took a back bench to the clearer relationship between group size and technology. But with the latter destroyed, might it be time for mobility to return to the limelight?

A new set of computer models reveals that we should pay more attention to being mobile.

It found that “encounter rates” were one of the key variables linked to technology. Meeting a lot of people was important for learning. You can “pinch” ideas from them all, build on them, and advance your toolkit. But how to ensure you meet a lot of people? Be mobile of course! Simulated groups that moved around more had a higher encounter rate. And as a result, they developed a better skillset.

An oversimplification

Ok. That’s also wrong. or rather, it’s an oversimplification. The real trick is meeting a lot of people. That gives you a lot of opportunities to learn. Being mobile is one way to ensure you meet a bunch. If you’re constantly moving around your environment you’ll bump into others. You can hang out and share skills.

Of course, there are other ways to encounter a lot of people. Like living in a large group. Or at least, a dense group where you’ll bump into others often.

The real secret isn’t being mobile or being in a big group. It’s being social. And humans have many alternate strategies for socialising. Like being mobile. The key point is that when you try and break this down into its individual strategies it falls apart. On its own, being mobile can’t explain our species success. Nor can large groups. But our ancestors were able to find a unique combination. By blending these strategies we succeeded as a species.

Crucially, we were able to vary that blend. Further north the environment is harsh. It’s cold, miserable, and hard to find food. The result is that large groups just aren’t an option. But the people living there can circumvent this problem by being mobile. Such mobility might not be necessary for those living closer to the equator.

Humans are successful because we’re great at making friends, regardless of the circumstances.

How mobile modern groups are, compared to their population density. The two are correlated, demonstrating how we flexibly adapt these variables to take into account changing circumstances, ultimatley keeping encouter rate the same

How mobile modern groups are, compared to their population density. The two are correlated, demonstrating how we flexibly adapt these variables to take into account changing circumstances, ultimately keeping encounter rate the same

References

Grove, M., 2016. Population density, mobility, and cultural transmission. Journal of Archaeological Science, 74, pp.75-84.

Henrich, J. (2004). Demography and cultural evolution: How adaptive cultural processes can produce maladaptive losses-The Tasmanian case. American Antiquity69(2), 197-214.

Vaesen, K., Collard, M., Cosgrove, R. and Roebroeks, W., 2016. Population size does not explain past changes in cultural complexity.Proceedings of the National Academy of Sciences, 113(16), pp.E2241-E2247.

6 thoughts on “Staying mobile was the secret to our evolutionary success”

  1. Sergio says:

    Nice blog, but all those pop-up don’t let me read your cool posts 😉

    1. Adam Benton says:

      They should only be set to appear once, so hopefully now you should have a much easier time

  2. leorivers says:

    Hermits and all their ideas and learning die with them. A sobering thought for me. Now I want to ask… if mobility is the key, isn’t the internet global mobility? And if so, is there evidence it is working as a species wide tool kit preservation and replenishment adaptation?

    PS: the pop ups keep a popping up. : 0

    1. Adam Benton says:

      Ultimately, the real key is frequency of engagement. So the internet could be a powerful tool for enabling such development. On the other hand, it isn’t necessarily the case. You could just live in an echo chamber, or send out statuses without considering other peoples’.

  3. harikrv says:

    “Humans are successful because we’re great at making friends, regardless of the circumstances.” A casual glance at the modern human society does not bear this out. Rather it appears humans are successful because we’re great at making enemies. One of the biggest technological advancements of the modern times – humans foray into space – was the result of the intense conflict and stiff competition between two nations who wanted to put the first man on moon.
    Most of the learnings and advancements throughout the history of mankind were fuelled by conflict. The very first advancement of them all – migration and colonisation of the earth – simply occurred, according to me, because of escalation of conflict with the increase in population that uprooted large groups of people and sent them far and wide across the face of the earth in search of peace. It is still happening today with migrant crisis being a widespread problem everywhere.
    Farming simply became a necessity when a group of strong humans enslaved the women and weaker males and looted all the food gathered by them. Per force this group had to grow their food or go hungry as they could not move about in search of food for fear of being attacked and looted. The whole arrangement of looting and slavery is very much alive today – only we call it economic system and support it with money instead of terror now.
    Weapons were developed and till today are being refined when a group of leaders (read politicians today) controlled the young men and turned their energies towards war with every neighbouring group through paranoid preachings. As conflicts escalated not due to real antagonism but due to the false propaganda of the wily leaders the ancient weapons race began. It continues to this day in the same format. Only difference is the enormously amplified killing power of weapons today. Do I need to illustrate this statement with the atom bomb story?
    Modern human society is almost unchanged in the fundamental structure for nearly over 50,000 years. If only we care to observe it very closely and dispassionately we can see this as clear as daylight. Searching for the modern human evolutionary clues among hunter gatherers living today is like blind men trying to describe elephants by touching their different body parts. Each will come out with a completely incompatible description with all the others.

    1. Adam Benton says:

      Whilst conflict does drive forward innovation; those leaps wouldn’t have occurred without people working together.

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