Wednesday, April 14, 2021

Periodic extinctions and more cheery stuff!

We are time travelers!

No, not in the sense of the teenagers who get 'time yanked' in my sci fi series for young adults: David Brin's Out of Time.  Or through space in my other YA series for teens, the High Horizon. (If you know any young folks - or you have a taste for mind-expanding adventure - you'll love these!)

Rather, today I want to discuss a different kind of time travel -- some ways in which we are getting windows into the past via science!

Earlier (recent) examples included Utzi the Iceman, who was discovered when retreating alpine glaciers exposed a neolithinc murder victim. Scientists were able to use the contents of his guts and pollen in his lungs to trace his exact path and meals and the season in which he made his final journey, till he was ambushed by some enemy. Incredible story!

Or the way genetic analysis told us about Chromosome bottlenecks in the past, including Mitochondrial Eve, the apparent mother of us all... and more recently evidence of a similar Y-chromosome bottleneck about 12,000 years ago, almost exactly when people made two technological breakthroughs associated with agriculture... beer and kings. And very likely the latter simply ordered the deaths of many males who couldn't control their use of the former!

But no, let's go even farther back!

== Here come those 'extinctions' again! ==

Ever more, we are using amazing techniques to penetrate what was a darkly hidden past.  For example, rhythms and 'cycles' or extinction that were part of Earth's meta-stable equilibrium... but of the sort that may have hobbled life's progress elsewhere. For example...

In EXISTENCE, I talk about how humans appear to have undergone a major cultural – possibly genetic – shift a little over 40,000 years ago, that included cave art, ceremonial burials and a vastly expanded suite of tools. (I assert it was just the earliest known in what would become a series of accelerating reprogrammings of the human operating system.) It’s also a time when many megafauna species... and our Neanderthal cousins... shuffled off the stage. 

Now comes a theory that magnetic pole reversals can stress an ecosystem and cause extinctions:One temporary flip of the poles, known as the Laschamps excursion, happened 42,000 years ago and lasted for about 1,000 years.” Accompanied by a major solar minimum, it may have caused the tipping point. Interestingly, my colleague Rob Sawyer goes with exactly this notion in his HOMINIDS series. 

The authors of this study go to the “42” thing, though, to connect with a different sci fi series. 

Oh, BTW: Earth’s magnetic field has weakened by about 9% over the past 170 years, and the researchers say another flip could be on the cards.”


== “Periodic” Extinctions are back on the table ==

In 2015 I re-posted my 1980s era article in Analog: "The Deadly Thing at 2.4 Kiloparsecs" along with updates, referring to theories for what might explain periodicity in Earth's major and intermediate extinctions. Now comes a revised estimate of extinction periodicity led by NYU’s Michael Rampino, who reiterates that widespread die-offs of land-dwelling animals – which include amphibians, reptiles, mammals and birds – appear to follow a cycle of about 27 million years.


The article says the next periodic comet drop isn't due for 20 million years. But track from the end of the Cretacous - 63 million years ago, if the cycle really was 27 M.y, then we would be 9 away from the next.

I've looked at the pattern currently listed here  and I don't think the 27M.y thing works at all, except as an average that posits a SINGLE cause. Especially, it doesn't look like a good fit for when our solar system plunges through the galactic "skirt."

But what if the triggers number more than one? Say TWO or THREE objects that pass nearby, disturbing our solar system, each with its own, longer periodicity... AND SOMETIMES THEY MISS, failing to leave a trace in the fossil record? Moreover, Suppose that the two - or 3 or 4 - trigger objects have somewhat different phases? 

I have to wonder if someone out there can program a fit to the listed extinctions with two or three different periodic triggers that sometimes fail to leave a trace. Including that latter element could be tricky. But it already looks to me as if some of the sums of adjacent intervals might show better periodicity.

My 'lapping" process (posited in the "Deadly Thing" article) could then be several causal objects in Galactic orbit, or possible brown dwarves in far solar orbit. In the former case, they'd be farther out from Galactic center than my 1st paper supposed, and thus pass sometimes much closer to us.

Of course, some of the extinctions may not have had a foreign cause... and the datings of the intervals gets foggier, farther back in time.

And now a splash of cold water. These other researchers claim to have used deep-learning systems to sift the data and found no clear timing relationship between the extinctions. 

== More reaching through time? ==

In EXISTENCE I posited the resurrection of the Neanderthal species in our near future. Are we already on our way? 

Neanderthal mini-brains! Working near UCSD, Dr. Alysson Moutri grown mini ‘organoids’ from both human neurons and others that were genetically altered with Neanderthal DNA. And the results are already so amazing that NASA agreed to fly a version of the experiment aboard the space station. (I was peripherally involved in that aspect of things.) “Organoids with the ancient NOVA1 gene also appear to mature more quickly and remain smaller than their modern counterparts, Muotri says." The neurons start to get more active at very early stages. 

These findings are consistent with the hypothesis that modern humans evolved big brains that continue to develop long after birth in order to navigate complex social systems. Of course I have revived Neanderthals as characters in Existence... But see also my own research into the role that neoteny has played in giving humans ever-young and agile minds. Well... some of us.

== And some space stuff! ==

While we’re talking about new tools to look back through time… Gravitational micro-lensing only works when three objects line up, our telescope, a distant star… and the object directly in between that’s doing the lensing by bending the star’s light as predicted by Einstein’s General Theory of Relativity. What’s amazing is… it works! With our new telescopes that can scan tens of thousands of stars at a time, we are spotting these events… and one revealed a small rogue planet, likely no larger than ours but cut loose from its origin system, doing the brief bending bit as it passed brifly through our line of sight! This may be important.

Curious. Is the universe getting… hotter? A team of international scientists compared the temperature of cosmic gas farther away from Earth (and, therefore, farther back in time) to younger gases nearer to our planet and to the present day. According to their calculations, in the past 10 billion years, the mean temperature of these gases has increased by more than 10 times. 

Remember that “monolith” discovered in an isolated red rock cove in Utah? Apparently the first published images were deceptive. It's a prism shape with triangular horizontal cross section. Making it much sturdier and less like 2001.  But the Interior Dept guys have a sense of humor. Anyway, apparently the “obelisk” discovered in the Utah desert has been there a long time. 

Are there others? In my novel EARTH, pyramidal obelisks have been placed to seem like the tips of a single, humungous tetrahedron sculpture embedded in the planet. Only one orientation lets all tips emerge on dry land; one must be on Easter Island... as I depict in the novel. And in real life a sculptor did it!


Rosanne said...

Interesting theory about multiple periodic triggers. Got me thinking about the math and programming required. I hope your post inspires someone.

I've read articles about most of the topics mentioned and got some updates here. Thank you.

Tim H. said...

Concerning the obelisks, I wonder if it made the hair on Greg Bear's neck rise a little... I think I'll pass on a reenactment of The Forge of God... If there's a choice.

Sojka's Call said...

I was thinking about the study you have suggested regarding looking back in time. Another far-fetched thought came to mind. Could a close call from a comet or asteroid cause an already unsteady gravitational field to flip the axis?

matthew said...

I don't get it - if magnetic pole reversals can take 22,000 years to complete, as this article suggests -

then when is the mass-extinction event?

Increased cosmic rays mean higher levels of cancer, so shorter lifespans?

If we are on a period of 47k years, but it takes 22k years to complete flipping, then our recorded history *just happens* to be during the ~50% of the time when we have a complete magnetic field?

What am I missing here? This doesn't seem to pass the sniff test.

Tony Fisk said...

re: Universe heating. It seems to me that the red shift caused by cosmic expansion would make more distant/older gas clouds appear cooler than nearer/younger ones. Hence an apparent warming? One assumes that the authors, and referees with a few more letters after their name than I do, have considered this point.

re: agriculture and beer and bottlenecks (brown ones?), the Australian aborigines make an interesting study. Firstly, while they've inhabited this land for at least sixty thousand years before Europeans. This suggests they had already separated from the peoples involved with chromosome bottlenecks; especially the Y-chromosome one.

European colonists, acting on the principle of 'Terra Nullis', have always tended to dismiss aborigines as poor degenerates who never progressed beyond the hunter-gatherer stage.

Except, they did.

Using the accounts from the diaries of the first white explorers of Australia, Bruce Pascoe's "Dark Emu" makes a pretty compelling case for claiming that many aboriginal societies practiced all the basic activities associated with agriculture. While fixed habitation was the exception rather than the rule, people were present in greater numbers than you would expect of simple hunter-gatherers. The signs of agriculture just didn't present in the way Europeans were used to. So, expecting subsistence living (an attitude Pascoe refers to as 'colonial bias'), even fairly astute people, like Major Mitchell, may have noted grains and root crops harvested, collected and stored in vessels, but without tilled fields, they didn't make a connection.

After sixty millennia of human habitation, Australia wasn't actually a wilderness peppered with farming lots. It was all carefully tended, and aboriginal agricultural practices might be said to have become embedded in it as they developed. Indeed, exploreres repeatedly referred to the garden-like nature of the landscape. I know this may raise the eyebrows of anyone used to the bark littering the ground of a eucalypt grove, but that comes from a lack of maintenance. As European pastoralists spread across the country, letting their flocks seek out, devour, and destroy the grasses and yam daisy patches, the tribes died of starvation and disease,* the landscape fell into neglect, and the fire fuel load increased. The first year of settlement was marked by Summer heatwaves that appeared to be every bit as searing as the ones that Sydney has had recently. Yet there was no fear of the conflagrations that now accompany such events.

No, aborigines didn't appear to have had beer, and the results were predictable (although they *did* have access to alcohol: see 'cider gum')

* and 'lead poisoning': the extent of which we are only just beginning to look into.

Tony Fisk said...

Multiple periodic extinction triggers sound similar to the way the various Milankovich cycles combine to cause ice ages.

I suppose it is possible that two triggers may combine on occasion.

One quibble I have: what form of energetic emitter would have lifespans measured in tens of millions of years?

... how about a medium size, normally quiescent black hole whose orbit brings it into close proximity to ours just as we are both passing through a dense and tasty area of dust (eg a spiral arm)? In fact, the density increases the likelihood of such an event: a waterhole effect.

Jonathan Armstrong said...

To extract periodic waveforms from time-series data, you need to apply a Fourier transform. This is well established mathematics. The FFT (Fast Fourier Transform), readily workable on computers, has been around for decades. It should be easy to apply that to species diversity numbers over the history of the Earth. This is so obvious it has surely been done already.

Robert said...

exploreres repeatedly referred to the garden-like nature of the landscape

Same thing happened when Europeans reached the Americas. Plenty of early accounts talk about how common edible fruits etc are, how you can ride a horse at full gallop through the forest, etc — they didn't realize it was a tended landscape. Consider terra preta in the Amazon, for example. Or how at first one of the signs that you were approaching North America was smoke in the air (from controlled burning in forests, which is what kept them clear of undergrowth and suitable for deer hunting as well as horticulture).

David Brin said...

Recent papers uggest Australian aboriginal tribes did similar things.

scidata said...

Controlled burning - Blackfoot wisdom.

Alfred Differ said...


Sorry I didn't get to this sooner in the last thread.

It’s certainly more natural than believing there’s a big, bad Godfather in the sky laying down the law(snip)

In my not so humble opinion, that sky godfather is more of the same, just taken to the limit. The Romans kinda copied the Greek pantheon of gods and had to contend with other cultures having their own. That led naturally down the path of multiple names/one god. Historically kinda common, but the Roman example is well known in The West.

If there’s no God or Logos, there’s no basis for…

I think this is also an error. The basis is there, it's just that it is human.

The fundamental error is one of those confusions equating map and terrain. I can imagine a spirit animating something, but that doesn't make it so. We can imagine a sky santa, but that doesn't make it so.

Why bother doing it? Well… it helps us organize our thoughts somewhat. I can imagine Lady Liberty or variations on Justitia (blind folded or not) or Prudentia (forward or backward looking) and use the icons to tell stories of ideals that don't really exist, but CAN if we chose to be loyal to them. However, it is an error to believe the existence proposition of these fabrications… except in Popper's World Three. They aren't World One or Two things, but that hardly matters.

The tale end of Hogfather explains this all rather well. Do You Believe?
That question is really about loyalty to an ideal… which makes it so… because WE make it so. Not because we create Sky Santa, but because we create the emergent behaviors that correlate to generate many of the same effects. Virtues are what we believe them to be as described in the stories we treasure both for entertainment and as explanatory models for the world around us.

My beef with ubiquitous animism is that it is entirely unncessary for it to be so damn ubiquitous. Science is making headway at showing just how mindless the Universe can be.

Alfred Differ said...

I've read up on the Y-chromosome bottleneck and was under the impression that it was closer to 8K years ago that it started while finishing shortly before recorded history begins. In other words, during a period where we were heavily dependent on domesticated grains that weren't all that domesticated yet.

Last time I checked, the bottleneck is an after-math story resulting from climate change (ice sheet retreat) forcing nomadic HG humans in some regions to adjust rather than move. Agriculture and animal husbandry are inventions of necessity rather than convenience and our average lifespans plummeted for those involved. Piss poor grains, partially domesticated animals, unadapted human genomes, and living in our own filth for long periods caused MASSIVE disruptions.

I know there are competing narratives, but I wasn't aware that the time window stretched far enough back in any of them to include a time very nearly as the ice retreat really got under way.

I HAVE seen all sorts of throw away, easy explanations for why the male/female ratio for people who never reproduced jumped from an average of 3-4 to 1 (like it is today) to about 17 to 1. Murder. War. Kings. You name it. They all seem a bit to easy for me to believe, but one of them stuck. Second and third sons aren't as likely to reproduce successfully if their fathers die young. THAT would do it.

Yah. Beer has been around a while. It's a technique that would enable more access to calories in piss poor grains. It really, really matters how far back the technique goes.

Alfred Differ said...

Sojka's Call,

Gravity fields don't really have an axis. They can have multipole moments (asymmetries) causing for some fun orbit changes, but those don't have to be arranged neatly with a rotation axis. They have to do with mass locations.

When you think about rotations, it's all about angular momentum... which does have an axis. Three actually. A comet flying by might use gravity to torque the planet. There is nothing unsteady about a planet's gravity, but its rotation axis might be if the planet is fluid enough in the interior.

Having said that, comets and pretty tiny. Maybe a dwarf planet would respond a bit, but not something the size of Earth or Mars. Earth responds to the torque our Moon creates, but our Moon is huge.

Larry Hart said...

Alfred Differ: helps us organize our thoughts somewhat. I can imagine Lady Liberty or variations on Justitia (blind folded or not) or Prudentia (forward or backward looking) and use the icons to tell stories of ideals that don't really exist, but CAN if we chose to be loyal to them.

That jibes with my perception of America. By remaining loyal to the ideals of equality and justice, we move reality in that direction, despite the fact that we've never accomplished the ideal. It is in that way that I perceive the former occupant of the White House as a traitor. Bad enough he himself was not faithful to the ideal, but he rose to power and maintained it by encouraging a large percentage of our fellow citizens to knowingly and proudly be unfaithful as well. He brought us to the climax of the movie Camelot in which the berserker knights are trampling the Round Table to bits under their horses' hooves.

Agriculture and animal husbandry are inventions of necessity rather than convenience and our average lifespans plummeted for those involved. Piss poor grains, partially domesticated animals, unadapted human genomes, and living in our own filth for long periods caused MASSIVE disruptions.

It would have been the late 80s that I came across a book on entropy whose author I no longer remember. That book made the argument that the move from hunter/gatherer to agriculture was not--as is often described--the result of a surplus allowing humanity to evolve upward to a higher state, but rather that of scarcity forcing humanity to devolve into lower one. The thesis seemed to be that the physical laws of entropy were present in human history as well as physics. That crises in history which cause civilization to abandon its older ways for replacements come about because the old ways are exhausted. Civilization adapts--for example, burning coal instead of wood once the forests are decimated--but the replacements are less efficient rather than more so. You can burn coal for heat in place of wood, but you can't build your house or a bridge out of coal, and furthermore, roads that were designed to carry cartloads of wood have to be reinforced to handle the weight of coal.

Why am I sadly reminded of the Enak character in Land of the Lost, realizing that he's accidentally travelled not to his past but his future:

I have made a grave error.
I have not travelled backwards in time, but forward.
The slestak are not my ancestors. They are the barbaric descendants of a race that could no longer keep its anger in check.
This is not my past. my future.

Tony Fisk said...

Not ever having done advanced studies of astrodynamics, it took me a while to figure out what it was with geodes. After all, it can be shown that all the gravitational effect of all the masses within a certain radius can be equated to a point source located at their centre of mass. If your spaceship is in orbit outside that radius (as one hopes it is!) it should be moving in a neat ellipse.
So why the wobbles?

The answer lies in the distribution and constraints on the masses involved. Earth's density is not homogenous and the distribution of mass is not symmetrical. That, in itself, wouldn't have an effect if it were all grains of sand milling around in a mad maelstrom of the N-body problem.* But that's not the case. The Earth is composed of solids lumps onstrained within a rigid matrix of crust and mantle which do not move entirely as gravity dictates. That is what gives rise to the wobbles.

* At least, not until grains started getting kicked out beyond your orbit, then you become part of the problem.)

Lorraine said...

I search galactic skirt and the search results are 100% fashion oriented all the way down. It's a designer label. Gotta wonder whether the brand gurus who came up with that were aware of the other galactic skirt (whatever even that is). What would be a good place to look concerning the other phenomenon?

Tony Fisk said...

*Ahem!* I was of course referring to 'geoids' in the previous post. (although 'geodes' aren't dissimilar in shape.)

Pappenheimer said...

I am sure that in the last few seconds before the Earth is boiled in hard radiation or sucked into a black hole, there will be people saying, "See? We shouldn't have allowed gay people to marry/eaten pork/stopped sacrificing our first born/poked badgers with spoons!"

Of course, that would be a time for a lot of conversions, some in directions you might not expect. I recall reading that the city fathers of Rome, faced with the first sack since Brennus went through back in the BC, gave up on the Christian God and made direct appeals to the Latin deities such as Jupiter and Minerva. The course of history might have changed a bit if the old family had come through...

Larry Hart said...


I recall reading that the city fathers of Rome, faced with the first sack since Brennus went through back in the BC, gave up on the Christian God and made direct appeals to the Latin deities such as Jupiter and Minerva.

The phrase "There are no atheists in foxholes," is used to demonstrate that secularism is a luxury of the comfortable, and that when one is really in need of assistance, one comes to understand that he relies on God.

To my ear, the phrase is equivalent to "A drowning man will grasp at straws." When one is desperate, one will try anything that has the remotest possibility of helping. A soldier trapped under enemy fire may try appealing to God for salvation--I mean why not?--but that doesn't mean that God's intervention is a real thing any more than the straws the drowning man grasps at will actually support his weight.

Robert said...

The phrase "There are no atheists in foxholes," is used to demonstrate that secularism is a luxury of the comfortable, and that when one is really in need of assistance, one comes to understand that he relies on God.

I know at least one soldier who has been under fire, taking casualties in a unit forbidden from returning fire, who was and remains an atheist.

As statements go, it's bovine byproduct.

scidata said...

I couldn't find any specific reference to deep learning in the extinctions timing article, but it's just as well. Making and stacking neural layers is great for building a Go player, but not for doing objective science IMHO. It's not nice to anthropomorphize Mother Nature. Impressing engrams onto silicon is a really lossy translation, as demonstrated by Dr. Daystrom's M-5. Gosh TOS was ahead of its time.

Paul451 said...

Re: Extinction cycles.

Our solar system routinely receives passes near other stars. ("Near" being defined as a few lightyears.)

Those which get close enough (less than two lightyears) to pass through each others Oort clouds would lead to an increase in comet impacts.

Those larger comet impacts which arrive at the same time as periods of increased volcanism or other potential climate disturbances might lead to major global extinction events.

[For example, a major impact on roughly the opposite side of the Earth from one of the supervolcanoes like Yosemite would create a shockwave focus at the mantle plume, turning it into a basalt flood event. The combination of impact on one side and massive volcanism on the other turning a minor regional extinction event (either event alone) into a global one. An example would be the Yucatan impactor and the Deccan Traps.]

The thing I find interesting is that more distant flybys happen more often than the time it takes for comets to descend from the Oort cloud to the inner solar system. (Tens to hundreds of thousands of years.) So the comets we see today are from several encounters ago. Same would be true of a major near flyby: We'd see the drastic increase in major comets only when the perpetrator has long fled the scene of the crime.

Re: 27 million year cycle.
We being pattern recognition creatures, can't help but see signal in the noise.

Paul451 said...

Tony Fisk,

Precession doesn't require unbalanced mass, it's just a natural side effect of angular momentum. Earth rotates too quickly for the unevenness of Earth's internal mass to explain multi-annual (let alone multi-millennial) precession cycles.

Paul451 said...

Aside: In around a million years, Gliese 710 should get to about a sixth of a lightyear of the sun. Deep within our Oort cloud. (And we within its.)

David Brin said...