Are humans on the verge of extinction? Opinion piece

[jim mcnamara]

https://www.scientificamerican.com/article/humans-are-doomed-to-go-extinct/
<note: edited a grammar faux pas and other atrocities...>
This piece is opinion, part Biology, and part sociology, so the best fit is in Discussion.
It is a short piece, do consider reading it.

It is a projection, not an instant doomsday forecast.

Kind of like 'we will get hit by a large asteroid- someday'. Why? because extinctions and asteroid impacts have happened a lot in our past. And are precursors to extinction building up?

The primary point is about overpopulation and resulting over-exploitation of resources for economic reasons. Population growth has decreased substantially since the 1968 peak point.
It is likely to continue going downward for several reasons. Lack of resources is a big one.
Sociological changes are another.

Most species do go extinct. We have, as mammal species go, very limited genetic diversity. Not good for long term survival of a species. We will likely go extinct the way most mammal species populations have done in the past and are doing now: grow too large too far past a changing carrying capacity, and then voila, a population crash -> species extinction. Lots of species have gone extinct in a fairly short time, since 1750. Why should humans be a complete outlier?

You decide.

Instead of my trying to enumerate all of the points presented in the article, please read it.
I can answer some questions hopefully.

 

[Jarvis323]

Humans are a special case. You probably can't extrapolate those models of population dynamics and extinction to humans.

Although we will probably cause a whole lot of other species to go extinct, and will likely transform Earth into a hellscape if we keep living like we do. And at some point Earth probably wouldn't be a livable place if we don't stop that.

 

[DaveC426913]

I gave it read.

At the risk of being glib, my opinion is that:
predicting the extinction of humans using animal extinction factors as precedent
is analogous to
predicting a bicyclist will inevitably crash into a tree at the bottom of a hill because rolling rocks crashed into a tree at the bottom of a hill.

Humans can steer their own course. The more dire their course might get, the more they are motivated to change their course. Humans aren't doomed to a passive response to their ecology.

The article makes broad implications, such as

- because sperm count is decreasing by a single digit per year - it will continue to do so - that it is not temporary, or cyclic - and that it will do so in perpetuity, despite anything and everything we can do.

- not only is our habitat decreasing ( in fact, a very small percentage of the Earth's surface is populated at all and there's plenty of room for expansion), but that we won't make it off-world and start new colonies.

I think I'd prefer to see a little more teeth in the arguments before I'll be too alarmed.

 

[Rive]

Has valid points, but missing just as many. The success of humanity is/was not due genetic specialization, what would made it prone to loss of habitat. Rather, it's based on cultural 'evolution', what makes it both potentially reversible and exceptionally flexible.
I think that as of now the survival/adaptation strategies in use has the widest variety ever (even with some of them indeed being dominant).

I can agree that some strategies (together with the carrying sub-groups) might suffer sudden collapse/shift.
In an unfortunate case (belonging to a likely affected group: viewing things from that point of view) it might be justifiably sensed as an impending catastrophe.

 

[russ_watters]

You decide.

His arms must be really tired.

 

[jim mcnamara]

It does fly in the face of Sociobiology ( E O Wilson) - the concept that the human genome does change very slowly but humans have highly modifiable complex hypersocial behaviors that allow for rapid responses to changing environments. Far faster than natural selection can change genomes.

 

[russ_watters]

I gave it read.

At the risk of being glib...

I think I'd prefer to see a little more teeth in the arguments before I'll be too alarmed.

My favorite part is how at the end of the article, after barely even mentioning extinction in the body, he concludes we're due for imminent collapse. K.

The only actual potential cause I see listed is habitat loss, which we don't have (we are only increasing our habitat).

 

[jack action]

I don't understand where this comes from:

In most countries—including poorer ones—the birth rate is now well below the death rate. In some countries, the population will soon be half the current value. People are now becoming worried about underpopulation.

Birth rates seem to be higher than death rates worldwide. Plus, how is halving the population in a country considered "underpopulation". Was the world "underpopulated" 50 years ago?

Is a population decrease necessarily means an extinction? 4000 years ago, they were only a few dozen million of individuals on Earth, and nobody talks about that period as being on the verge of extinction, quite the opposite.

Finally, if a number goes down, how do we know it won't stabilize or go up again?

Trying to predict human extinction is a pointless exercise at best.

 

[Jarvis323]

Trying to predict human extinction is a pointless exercise at best.

Why?

 

[DaveC426913]

Why?

Er. See posts 2 through 8? *(including one by you?)

Not trying to be a j*rk but didn't we just cover that?

(The short answer is: because we have a dataset of one. i.e. no precedent by which to compare)

 

[BillTre]

Its an interesting article. Although the possibility of human extinction is not unreasonable, I have problems with how he thinks it might happen. I also don't think he has explained his extinction mechanisms very well.
(I consider Gee a kind of provocateur, based on what I have read of his before. It may be that is how he sees his job as a Nature editor.)

His mechanisms:
Stress and crowding reduce fertility through hormonal mechanisms or habitat loss or degradation.
These are reasonable mechanisms and are fairly well known from animal studies.
On the other hand, in animal populations, overcrowding usually results in cycles of population growth and crashes without going extinct. To some this is a natural (Malthusian) form of population control. As overcrowding decreases, stress is reduced and fertility returns.
Environmental degradation or loss is a more serious problem, however I don't think it alone will lead to extinction unless the world just becomes toxic to human life (or reproduction). However, it appears to me that human populations have been quite successfully exploiting more and more of the Earth's environments available for their use.

His use of extinction debt is puzzling to me. I had not hear the term before. In a paper linked to by the article @jim mcnamara cited, extinction debt was proposed as a basis for species with patchy populations (present in some areas, but not others). I don't think of the human population that way. I'm not sure it really applies.

Reduced sperm viability: it may be happening, but I think a technological fix could prevent a complete population crash to extinction. I would not be surprised if it is possible, in 10 or 20 years to grow human sperm derived from induced stem cells in a dish. This along with supplies of frozen sperm would provide some level of reproduction, which would prevent extinction.

Other than things like big impacts (which could also have technological fixes), the most likely kind of problem would be not the direct destruction of humans or their ability to reproduce, but the destruction of the ecosystems in which we live and upon which we rely for food and shelter, etc.
When there have been really big extinction events in the past, it was due to the basis of production and the distribution of its benefits through the ecosystem breaking down. This can result in huge numbers of species going extinct.

The end Permian extinction resulted in:

the extinction of 57% of biological families, 83% of genera, 81% of marine species[8][9][10] and 70% of terrestrial vertebrate species.[11] It was the largest known mass extinction of insects.

The extinction that killed the dinosaurs (except birds) resulted in:

With the exception of some ectothermic (ectothermic means cold blooded animals which use about 1/10 the amount of food/energy per body mass of warm blooded species) species such as sea turtles and crocodilians, no tetrapods (tetrapods are four legged vertebrates: amphibians, reptiles, birds, and mammals) weighing more than 25 kilograms (55 pounds) survived.[5]

In both these cases, food chains, going from primary producers (like plants) to other organisms, were no functional. Without sufficient food/energy, many species, large and small, went extinct.

Rather than loss of habitat, I think this is a much more likely way for humans to go extinct. It would also be much more difficult to mitigate with technological fixes.
This to me is the ultimate challenge of climate change.

Another way to go extinct could involve the evolution of new human species after which the original went away. The original species might then be gone, but descendants would still be around. Not so drastic..

 

[hutchphd]

I believe that although we humans are only marginally more self-aware than our fellow and previous travellers here on planet earth, we are not necessarilly constrained by precedent events.
As a dismal and obvious example, no previous species has generated, over a span of a handful of centuries, the capability for self-annihilation represented by our stockpiled nuclear weapons. This is but one distinction that differentiates our possible extinction.
So while I am not particularly sanguine about our chances (I think we may have peaked in 1969...lucky for me), any attempt to extrapolate from previous species events seems foolhardy.
And the dinosaurs had no inkling of personal demise and certainly no T S Eliot...

 

[Jarvis323]

Er. See posts 2 through 8? *(including one by you?)

Not trying to be a j*rk but didn't we just cover that?

(The short answer is: because we have a dataset of one. i.e. no precedent by which to compare)

We just covered why we thought this person's opinion about human extinction is probably invalid. We didn't prove that it is impossible to predict our extinction.

 

[DaveC426913]

His use of extinction debt is puzzling to me. I had not hear the term before. In a paper linked to by the article @jim mcnamara cited, extinction debt was proposed as a basis for species with patchy populations (present in some areas, but not others). I don't think of the human population that way. I'm not sure it really applies.

I'm not sure if this is related (and if it is then makes for a bad argument ) but I have heard of a theory that some populations are considered genetically extinct even when there are plenty of individuals in the wild.

Passenger pigeons might be one example. If they will only breed when the the population is above a certain number - which could be in the millions. So, even if there are millions of passenger pigeons in our skies, they might already be extinct and not know it.

This might be the case with cod/haddock shoals as well. While we encounter shoals of millions, they may not be sufficiently large to trigger breeding behavior, which would result in an unstoppable feedback loop leading to extinction.

(This would be a terrible argument, since humans are triggered to breed even in a flock of two, and - not to put too fine a point on it - even a flock of one).

 

[BillTre]

I'm not sure if this is related (and if it is then makes for a bad argument ) but I have heard of a theory that some populations are considered genetically extinct even when there are plenty of individuals in the wild.

I have not heard this one. Would be interested to see how it was supported.
I find it hard to think of how this might be literally made to happen. Geneticists can due some amazing things in breeding experiments, but that involves intentional trickiness and highly manipulated homogeneous populations. That wouldn't occur in nature.

It might be possible to be genetically dead in the future if some genetic element were going crasy in the genome and causing numerous genetic problems, like insertions or translocations, continuously. Its not completely unheard of because there have been ocassional genome invasions by genetic elements in the past.
One of their signatures are the different classes of repeated elements found in the genomes of different clades.

This might be the case with cod/haddock shoals as well. While we encounter shoals of millions, they may not be sufficiently large to trigger breeding behavior, which would result in an unstoppable feedback loop leading to extinction.

If this were the case, then it would be a very no-adaptive situation for that species.
Any variants in the trait (not breeding if there is no big flock) would be highly selected for (because they are breeding) and would increase in the proportion of the population.
A problem might be if the genetic variability were too small, than the variability might not provide useful options to select.

 

[Keith_McClary]

Why?

If you were right, you would be famous. Everyone would know your name!

 

[fresh_42]

If we say humanity or mankind we apparently assume the technologically advanced part of us. There are really many reasons this branch can go extinct (solar mass eruptions, asteroids, gamma rays, war about water or food, etc.). However, we are so many, that I suspect that some of us will survive under which circumstances ever. This might not necessarily be the technological part of us.

 

[DaveC426913]

If we say humanity or mankind we apparently assume the technologically advanced part of us. There are really many reasons this branch can go extinct (solar mass eruptions, asteroids, gamma rays, war about water or food, etc.). However, we are so many, that I suspect that some of us will survive under which circumstances ever. This might not necessarily be the technological part of us.

Oh God. The Preppers will inherit the Earth.

 

[fresh_42]

Oh God. The Preppers will inherit the Earth.

Unlikely. But if we who heavily rely on electric power will be gone, then oceanic, tropical and arctic ecosystems have a chance to recover. I thought about Inuit, Chukchi, and Amazonian tribes.

 

[256bits]

- not only is our habitat decreasing ( in fact, a very small percentage of the Earth's surface is populated at all and there's plenty of room for expansion

It is not just the immediate space one does occupy as an individual, but the space needed to support one's presence on Earth and lifestyle. Space is needed for the technological, cultural, energy consumption ( individual food, heat and shelter ) and economic niceties that one enjoys, and that can come only from the limited natural ( not human ) ecosystem and the geological system.

Right now, with approx 8 billion people and a surface area of 5.1 x 10⁸ km², the human density is 15.3 per km² (40 per sq. mi.).
For the land density ( 30% of the surface area ) the human density becomes 50 per km² (129 per sq. mi.). Take a plot of land 150m square and that is what is presently generally supporting one person. About the size of a football stadium.

 

[256bits]

Unlikely. But if we who heavily rely on electric power will be gone, then oceanic, tropical and arctic ecosystems have a chance to recover. I thought about Inuit, Chukchi, and Amazonian tribes.

Perhaps he is correct then for sub-species extinction, sub species being the different cultures that humans have evolved to invent. Sub-species not being the correct word, maybe sub-cultures. In that case, the present high technological sub-culture could go extinct quite easily, with the result in multiple die off and erasure of knowledge. Humans genetically would not go extinct but would start over as possibly hunter-gathererer once more. Would they, or could they, make technological progress again. Possibly, and to what extent. All the more easily mineral resources have been mined out by this run of humanity.

 

[Jarvis323]

So when the human technological subculture goes extinct, what about our AI? Does it go on colonizing the galaxy independently from us. Do we coexist with it on Earth?

 

[PeroK]

The article as it stands is a piece of total nonsense. If we imagine that whales, say, are as intelligent as humans, what can they do with that intelligence? The answer is almost nothing, because they are completely trapped in their natural environment. They cannot build shelters, grow crops, domesticate other sea creatures or in any significant way change the course of their survival. If their natural environment or food supply disappears, then there is nothing the whales can do about it.

Humans, however, have undergone an enormous process of cultural evolution, continually adapting to new environments. In fact, The Ascent of Man by Jacob Bronowski begins by making this very point:

We could become extinct for several reasons, but we have ascended past the stage where it could happen for the same reason it happens to other mammals. There's no inevitability about it and certainly not in the short term for the reasons given in the piece, which I'm surprised was published. A high-school student could write a better piece on the issue of potential human extinction.

 

[gleem]

Humanity is the only life form that can control its destiny. It might suffer tremendous losses on occasion but only physical destruction of the Earth or an event producing an earth-wide hostile environment incompatible with human life will extinguish the human race. Human biological and sociological diversity will produce populations that will adapt to most challenges to survival. Clearly, it is impossible to put a timeline on humanity's existence. I don't believe that there will not be some bad times for humanity but extinction is way at the end of the deck.

How low can a population get and still survive? Probably in the neighborhood of 3,000+. A cataclysmic event will most like leave numerous individuals that can cope and form many groups of this size.

An emerging rule of thumb is that when a population starts to dip below several thousand individuals, it has a high likelihood of going extinct..

https://phys.org/news/2018-03-populations-pair.html

If birth rates continue to decline at the present rate then it will still be about 150 years before we reach zero growth. The likelihood of that may well be forstalled or eliminated by AI and sustainable power if our economic systems properly adapt as it reduces the need for human labor and people choose to have more children when the economics of raising children is no longer an issue.

As far as some calamitous fertility problems developing is concerned, it would seem very unlikely that a scenario would evolve as depicted in the TV series " A Handmaidens Story".

 

[Jarvis323]

How low can a population get and still survive? Probably in the neighborhood of 3,000+. A cataclysmic event will most like leave numerous individuals that can cope and form many groups of this size.

Maybe or maybe not. Disease can crush that hope. And cataclysisms can come with die offs of plant and animal life and subsequent lack of food. Humans now generally have poor survival skills in nature in general, and that would probably get worse over time. Unlike our ancestors, most people now couldn't craft arrowheads and bows, or start fires. And we have no significant amount of fur. We rely heavily on technology to survive and 99.99 percent of the people have no clue how to make that technology. Take away electricity for a few days and people are already in a state of emergency. Take away food production capacity suddenly (say the sun is blocked) and people will scour the Earth until every last animal and edible plant is gone, and then begin eating each other. Then almost everyone would starve.

Over time we'll become less and less fit biologically in terms of resistence to disease. Let us evolve with dependency on advanced medicine for 10,000 years, and let the super diseases evolve in competition with our medicine. Then take the medicine away. Then what happens? Does it help that by then the water might not be drinkable? And the air might be toxic?

The current course of humanity is absolutely not sustainable and puts us in very precarious situations. Whether we survive is likely a matter of whether we change.

 

[russ_watters]

...cataclysisms...

Natural cataclysms are near completely unpredictable, so there is little value in speculating on the inevitability of our extinction with them as a trigger - and certainly not with any depth/detail. Yup, if an asteroid the size of Texas hits Earth we'll likely be wiped out. Sure, ok.

The current course of humanity is absolutely not sustainable and puts us in very precarious situations. Whether we survive is likely a matter of whether we change.

That's far too vague to be of value. Human-caused disasters have to have cause and effect. There has to be mechanisms by which the thing we do leads to our demise. Just saying the path is not sustainable doesn't provide a reason why we might go extinct. Do you have one?

 

[fresh_42]

There is a natural cause that will make Earth as we know it inhabitable, so there is a natural upper bound for our existence on earth. I'm just wondering if a direct hit by GRB is survivable.

 

[russ_watters]

If birth rates continue to decline at the present rate then it will still be about 150 years before we reach zero growth. The likelihood of that may well be forstalled or eliminated by AI and sustainable power if our economic systems properly adapt as it reduces the need for human labor and people choose to have more children when the economics of raising children is no longer an issue.

That's the part that annoyed me most. Much of the article is about population decline, implying he thinks that decline = extinction, but that isn't any more true than saying rising population means it will keep rising infinitely. It's over-use of a grossly oversimplified mathematical model (at best). And even then he doesn't provide any reason whatsoever for his concluding statement that he thinks collapse, not just shrinkage, is "coming soon". It's like he was trying really really hard to justify a his pre-judged conclusion but he didn't get there so instead he just jumped the shark.

 

[russ_watters]

There is a natural cause that will make Earth as we know it inhabitable, so there is a natural upper bound for our existence on earth. I'm just wondering if a direct hit by GRB is survivable.

Could you elaborate on that "upper bound" is? Are you talking about the frequency/likelihood of a GRB hit?

 

[fresh_42]

Could you elaborate on that "upper bound" is? Are you talking about the frequency/likelihood of a GRB hit?

I meant the sun's lifecycle and its increasing radiation which provides an upper bound.

AFAIK is the likelihood of a GRB nearby very small. So if it would occur - despite all odds - and it hits one half of the Earth's surface, does it affect the other half, too, and would it make the entire globe inhabitable?

 

[gleem]

It is my understanding that a concern of GRB of high intensity is the destruction of the ozone layer letting much more of the Sun's UVB reach the Earth's surface. Since the radiation is contained in a cone of up to 20 ° there is less than a 1 in 129 chance of the Earth being it randomly. If the beams have a preferential direction say perpendicular to the plane of the galaxy then it would be even smaller.

But we have been alerted to the demise of the Earth anyway. For all we know a GRB will hit us at

 

[Jarvis323]

That's far too vague to be of value.

Or maybe it's the single most important truth for all of human existence ;)

 

[jack action]

We rely heavily on technology to survive and 99.99 percent of the people have no clue how to make that technology.

0.01% of 7.8 billion is 780 000 people that know how to make the technology. Even if 90% of the world population is suddenly and evenly wiped out, there will still be 78 000 people - among 702 000 other people - to continue making the technology. It is still large enough of a population to keep going on.

Destroying 7.8 billion people completely is very, very difficult.

Take away food production capacity suddenly (say the sun is blocked)

The sun being blocked is pretty much the end of life on Earth.

Let us evolve with dependency on advanced medicine for 10,000 years, and let the super diseases evolve in competition with our medicine. Then take the medicine away. Then what happens?

It's pretty much improbable that there will be such a disease that can wipe out billions of individuals, scattered across the globe, of the same species. A disease killing its host will die itself.

The current course of humanity is absolutely not sustainable and puts us in very precarious situations. Whether we survive is likely a matter of whether we change.

If what we do is not sustainable, the changes will happen by default (whether we undergo these changes willingly or not). That is still not an indication of extinction.

Doom scenarios for extinction such as diseases, pollution, or food deprivation are great for sci-fi, but very unlikely because the problem tends to go away as the population decreases. The system is so complex that when you change a variable, there are hundreds, maybe thousands of other variables that will also change to balance things out, most of the time in a very unpredictable way.

 

[Jarvis323]

The sun being blocked is pretty much the end of life on Earth.

It's happened several times in the last few million years.

 

[PeroK]

Doom scenarios for extinction such as diseases, pollution, or food deprivation are great for sci-fi, but very unlikely because the problem tends to go away as the population decreases. The system is so complex that when you change a variable, there are hundreds, maybe thousands of other variables that will also change to balance things out, most of the time in a very unpredictable way.

When you look at the arguments for these scenarios they have a familiar pattern of:

1) Human society relies on X (because it's cheaper or easier to get than Y)
2) X is running out
3) When X runs out, humanity will end

Where, actually, we have:

3) When X runs out we'll be forced to use Y instead.