Talks, field trips and events organised by west country geological organisations are publicised on this blog. Discussion about geological topics is encouraged. Anything of general geological interest is included.
Earth Logs, a favourite source of mine, in THIS ARTICLE has brought THIS WONDERFUL ARTICLE to my attention. It has, in reasonably clear fashion, all you need to know about life before the Cambrian.
Was there a Cambrian Explosion of life - perhaps not. The article has lots of pictures and references to follow.
Organisms named Fractofusus cover the sea floor some 560 million years ago, in a reconstruction of fossils from Newfoundland, Canada. Credit: Dr Charlotte G. Kenchington
Pterosaurs - flying dinosaurs - were around for 150 million years and over that time their flying eficiency improved by 50%. Easy to say but how do you prove it? In THIS PAPER Mike Benton shows how it was done.
Pterosaurs increased their flight efficiency over time – new evidence for long-term evolution
With a wingspan of 12m–15m, Quetzalcoatlus was one of the largest flying animals that ever lived. Indeed, it seems astonishing that such monsters could fly at all. Yet over a period of more than 150 million years, pterosaurs (the flying cousins of dinosaurs) became increasingly efficient at flying as they evolved from small animals the size of a starling to become giants of the sky.
Our new research shows that pterosaur flight efficiency improved by 50% over the period from 230 million years ago to their extinction 66 million years ago. This enabled them to fly for over much greater distances for long periods of time.
This may seem like a remarkable or even foolhardy conclusion to draw from a study of fossils, but we have developed methods to extract the data. What’s more, this finding goes to the roots of how Darwinian evolution works, suggesting that lifeforms can continue to adapt to their environment over very long spans of time.
Pterosaurs were active, warm-blooded animals, insulated with whiskery feather-like structures all over their bodies. They flew using leathery wings made from skin supported by an especially long fourth finger that extended from their elongated arms.
To calculate the efficiency with which different pterosaurs flew, we first needed to know how heavy they were. So we made estimates based on the size of 16 species for which we have relatively complete skeletons and cross-checked our figures with those of birds and bats to make sure they were reasonable.
A flock of Rhamphoynchus in flight.Mark Witton/University of Reading, Author provided
We also estimated the basal metabolic rate (BMR, the energy expended by an animal when at rest) for each pterosaur species from a large sample of BMR and body mass measurements for birds. We were then able to create an “efficiency of flight index” based on estimates of how much energy each species would have needed to travel at its ideal speed, just fast enough to defy gravity, relative to its body mass.
By modelling reasonable values for other species, we came up with figures for 128 different pterosaurs, which we then mapped on an evolutionary tree that showed how flight efficiency changed over time as the species evolved. We found that for all pterosaurs except azdarchoids, there was a significant increase in body size, wingspan and flight efficiency. We used what’s known as a “Bayesian modelling approach” that repeated and improved the analysis billions of times, considering all possible combinations of all possible sources of error.
Body mass rose from a mean of 0.6kg in the Middle Jurassic epoch to 6.05kg in the Late Cretaceous. In the same time, mean flight efficiency increased substantially. Much of this increase in efficiency was related to increasing body size – bigger pterosaurs naturally flew more efficiently. But once body size was excluded, we found that flight efficiency still increased by some 50%.
The azhdarchoids, a group of pterosaurs with very long legs and necks, seem to have bucked the trend and showed decreasing flight efficiency with increasing body size. They were evidently following their own evolutionary route to excessively huge body sizes, meaning that evolving to become larger gave them other advantages on the ground and they became less dependent on flight to get around.
The azhdarchoid pterosaur Hatzegopteryx, with a 10m wing span, was not a great flier.Mark Witton/University of Reading, Author provided
A test of Darwinian evolution
Our findings don’t just tell us something interesting about pterosaur evolution, but provide useful evidence about evolution itself. A core assumption of Darwinian evolution is that adaptation by natural selection drives successful organisms to improve in some way. Within populations, the fittest organisms survive, and their fitness is measured not only in their successful adaptations but also because they breed and pass on their successful genes.
An important question for scientists has long been whether we can measure these improvements through longer spans of time, say between species and over millions of years. In arms races between predators and prey, the lion runs faster to catch its prey, but the wildebeest runs faster to escape. But they don’t keep evolving faster and faster speeds forever – ultimately they are limited by material constraints.
In 1973, evolutionary biologist Leigh Van Valen put forward his “Red Queen hypothesis” of Darwinian evolution to try to resolve this conundrum. Van Valen realised that the environment in which an organism lives is not constant but is changing all the time. And so the organism has to keep evolving and adapting just to maintain its status quo. As the Red Queen in Lewis Carroll’s Through the Looking-Glass said: “It takes all the running you can do to stay in the same place.”
Our results suggest that organisms can become more efficient over a very long period of time. The Red Queen hypothesis likely explains most situations where organisms are in some kind of balance with each other within their ecosystems. But our work shows that actual net improvements in physical performance can happen. This perhaps supports a central assumption of Darwinian evolution that has been nearly impossible to test until now.
This is not likely to affect you in the UK - unless you are in a train near Stonehaven! - but good to know for visits to more exotic parts. THIS ARTICLE summarises THIS LONG ARTICLE which goes into exhaustive details of how a landslide can kill you.
The advice is straight forward.
Before
Check if there are potential dangers of a landslide.
Live in the downhill side of a house.
During
Move upstairs
Go to interior, unfurnished areas
Open downhill doors and windows
After
Make noise so rescuers can find you
Don't
Open a door out of curiosity
Shelter beside large furniture
The article goes into much more detail, giving reasons for the survival strategies.
P.S. In the accident near Stonehaven it wasn't the landslide that caused the deaths but the train being derailed when it ran into the relatively small amount of landslide debris.
Geomorphology was never like this in my day! A correspondent has brought THIS ARTICLE to my notice - thank you! It is based on THIS JOURNAL PAPER. The research area was Bhutan.
Rain erodes mountains. Does the removal of material cause mountains to rise because of isostasy? This has been discussed for ever - or so it seems!
The papers describe an attempt to measure this. As you might expect, this is not easy. relief and rainfall at fairly easy to measure but erosion rates are more difficult. The method used here is to measure chemical changes in quartz sand caused by cosmic rays. This goes by the name "detrital cosmogenic nuclide erosion rates".
Presumably fewer changes mean faster erosion. The longer the sand is on the surface the more cosmogenic nuclides and slower erosion.
It is thought that erosion rates are roughly equal to uplift rates as the landscapes are thought to be in equilibrium.
The papers quantify how rainfall affects erosion rates in rugged terrain. And that tectonic activity is affected by rainfall!
The geomorphology i was taught was a descriptive subject. Reading this paper shows thait has changed! But you still get to go to interesting places.
Many organisations have been holding "Virtual Meetings", mostly quite successfully. But I came across THIS REPORT in the Guardian which tells of a less satisfactory event.
Apparently the organisers for the US-based Society of Vertebrate Paleontology used a filter which rejected certain words considered unsuitable. The words suppressed might be unsuitable in many circumstances but not when discussing ancient life.
Not wishing to shock my readership I will not repeat the naughty words - those of you of sufficiently strong minds can read the article. And NO giggling!
A correspondent brought THIS ARTICLE to my attention. It gives a very readable introduction to the rather unusual limnology of Lake Kivu, on the border between Rwanda and the Democratic Republic of the Congo.
The lake is large and the water is stratified. The surface water (the uppermost 60m) is normal. The rest (down to 460m) is full of carbon dioxide and methane, coming from hot springs in the bottom of the lake. And the two layers do not mix.
The unusual separation of layers of the lake is at the core of its volatility (Credit: D Bouffard & A Wuest/AR Fluid Mechanics 2019/Knowable Magazine)
There was a similar situation at Lake Nyos in Cameroon. There was little or no methane here but in 1986 the CO₂ was released (by a landslide) and 1,800 people suffocated. This is unlikely to happen at Lake Kivu, but the lake is constantly monitored.
But lately the methane is being exploited as a fuel source to generate electricity - something which is badly needed in the area.
The article gives you far more information than I have - well worth reading!
The following article has been republished from The Conversation. A link to the original can be found at the bottom of the page.
Do you like this means of quoting the article? - let me know.
Two Bristol researchers used X-rays from synchrotron sources to count the growth rings of fossil teeth of early mammals from South Wales to gauge their ages and blood flow. And discovered that they were between reptile and modern mammal ranges.
Did warm bloodedness come later?
AND a correspondent has brought THIS RELATED article to my attention - Thank You!
Fossilised teeth reveal first mammals were far from warm blooded
Warm blood is one of the key traits that led to the success of mammals as they evolved from scurrying beneath the feet of dinosaurs to spreading into the wild and wonderful collection of animals we know today. But our new research, which involved X-ray scanning hundreds of fossilised teeth, suggests the first mammals were more like cold blooded reptiles, and that warm blood evolved much later.
Warm blood helps us maintain our body temperature regardless of our environment, allowing us to gather food at night and in cold climates, and helps us stay active for longer than our cold blooded relatives. However, exactly when, why, and how this evolved is still poorly understood.
We know from tiny fossils of bones and teeth that mammals first evolved over 200 million years ago, and had many of the traits we associate with mammals, such as specialised chewing teeth and bigger brains. But the physiologies (how an animal’s body works day-to-day) of these animals is difficult to estimate using traditional methods, as this relates to soft organs that aren’t usually fossilised.
Our new research, published in Nature Communications, now offers a glimpse into the physiologies of the first mammals, by pioneering X-ray imaging to count growth rings in their teeth and measure blood flow through their bones. Although it had previously been assumed that even the earliest mammals were warm blooded, this research suggests that they still had some way to go before developing warm blood and its benefits that we enjoy today.
Long lifespans and slow metabolism
Working with a 20-strong international team of scientists, we have estimated the lifespans of the earliest mammals for the first time. This was done by X-ray scanning hundreds of fossilised teeth found in south Wales of two tiny mammals, Morganucodon and Kuehneotherium, from the Early Jurassic epoch.
High-resolution scans performed at powerful “synchrotron” X-ray sources in Switzerland and France allowed us to count annual growth lines preserved in the fossilised cementum of these teeth. Cementum is the little-known tissue that anchors mammal tooth roots to the jaw, recording every year of an animal’s life by growth lines that can be counted like tree rings to estimate lifespan.
X-ray image of tooth cementum from Morganucodon revealing growth rings.University of Bristol, Author provided
These lines are counted in living mammals by grinding teeth down into thin sections that can be studied using microscopes. As this destroys the tooth, we could not do this with precious museum fossils, and so we used X-ray imaging. Counting rings in our fossil mammal teeth gave a lifespan of 14 years for Morganucodon, and nine years for Kuehneotherium.
These are significantly, and surprisingly, longer lifespans than those of similar, shrew-sized mammals living today whose wild lifespans rarely exceed two to three years. This suggests a dramatically slower metabolism, or pace of life, than living mammals, and instead more closely resembles that of living reptiles.
Low activity levels
The size of the openings for the major blood vessels running through an animal’s limb bones is known to be proportionate to the levels of sustained activity (such as hunting and foraging) that they are capable of: smaller size suggests lower activity levels.
When we measured this in the femur of Morganucodon, we found that, while smaller than living mammals, they were also higher than those of living reptiles. This suggests that early mammals had an intermediate ability for sustained activity, between warm blooded mammals and cold blooded reptiles.
University of Bristol
This combined approach of studying the lifespans and activity levels of early mammals provides the first direct window onto several aspects of how they lived. We can see that our earliest relatives kept a much slower pace of life, but had definitely started on the road to the active lifestyles of living mammals today.
We shall continue these studies through the early mammal fossil record, to shed light on the first steps towards the modern mammalian lifestyle, and when we truly became warm blooded.
A correspondent has brought THIS PAPER to my attention. We used to think that the Alps were built by the Adriatic plate pushing against the Eurasian one, pushing lots of stuff to create the mountains.
But the seismicity of the Alps is characteristic of expansion, not of the compression that you would expect. The paper tries to explain this and other phenomena.
The explanation given that, as the Adriatic plate, especially the continental part abutted the Eurasian plate (30 Ma ago), the upper, lighter, crust of Eurasia, separated from the lower, denser mantle. Being lighter it surged upwards (no doubt, at a suitably stately pace) to form the Alps.
The sinking of the lithosphere sucks the Adriatic plate northwards.
Reading the article may help to understand it - I am struggling with it. Where do these wonderful nappes come in?
The Journal article may help but you need some form of subscription to access. THIS gives the abstract. But a "high-resolution, rheologically consistent, two-dimensional visco-elasto-plastic thermo-mechanical numerical model" seems a bit above my pay grade!
THIS ARTICLE gives an interesting perspective on genetics. It is well known that most of us have some fragments of Neanderthal DNA in our genome. This happened when Anatomically Modern Humans (AMH) left Africa and interbred with Neanderthals in Eurasia. A few Neanderthals went the other way but most Africans have very little Neanderthal DNA.
Fast-forward a few millennia and Covid-19 arrived. And it was found that if you had a section of code on chromosome-3 you were more likely to have a severe (unfortunately often fatal) reaction to COVID. And this section of code is very similar to that in the Neanderthal genome!
