 |
P T Boundary
Yet again, an excellent programme. I look forward to Melvyn's enlightening discussions every week. For me 'In Your Time' is the highlight of the week - the antithesis of those programmes with annoying presenters who cause me to hastily switch off. Sheilam
Tim Jordan - P-T boundary
Though the consensus on the programme was that the extinction was not caused by an asteroid impact, surely the correlation between extinctions (P-T and K-T) and the major intervals of Galactic Tidal Cycles (with increases in asteriod activity) suggests otherwise. Furthermore, I understand there is evidence of impacts from that time, notably at the point on Pangea which is now the (separate) tips of S. America, S. Africa and the Antarctic Peninsula, but also at Araguainha Dome on Brazil, Kursk in Russia, and Gow Lake in Canada.Further discussion on this point would be most enlightening, perhaps "GTC; Fact or Fiction" as a separate programme?Thanks
David Edwards The Permian-Triassic Boundary
An excellent programme the experts were all very clear in their expositions of the facts and arguments. Who would have thought that such an 'ivory tower' discussion of such remote events would have important messages for us today.What a pity the technologists and the politicians who make the policies on such matters as wasteful bio-fuels and economists who continually spout the mantra of continually 'expanding markets and consumption' were probably not listening!Global warming from gigantic volcanic upheavals is one thing. The threat of coming ecological devastation is purely man made. We can rush blindly on towards possible extinction, or pause to rationally and scientifically, examine the various strategies and possibilities (including nuclear)open to us. The dinosaurs (as a group) extended over 60 million years, the several humanoid species (including H.neanderthalis and H. sapiens)have only been around some 3-4 million years. Yet we tend to think of the dinosaurs as 'inferior' creatures. Not in terms of survival probably!A possible follow up programme on 'global warming' could be planned Melvyn - surely an issue 'in our time' if ever there was one?
Alick Bartholomew --The P-T Boundary & Climate
Melven Bragg passed on in his weekly letter a remark of contributing archeo-climatologist Jane Francis: "Cutting down the Amazon forests to grow bio-fuels was utterly ridiculous". This is an enormous understatement. This precious eco-system is much much more than about CO2 emissions. The tropical rainforests are probably the most crucial part of the world's total eco-system in that they control the planetary climate, moderating the extremes of equatorial and temperate latitudes. With their destruction, the hotting up of the equatorial and cooling of the temperate/polar regions, not to mention much more violent weather, are likely to make the environment uninhabitable for the present large human populations and for biodiversity. It is the feedback system that could so magnify current climate change to result in a species loss similar to that of the P-T boundary, with comparable implications.
In Our Time general thanks
I just wanted to post the whole team a big "thank you" for a mind expanding series. Indeed series after series. I scroll down and see people hugging their particular world view (see astrology) and think yes but we have to have open minds. If we don't we are just a stupid species awaitng our Dawinian fate. All things must pass but boy did we have some fun. Thank you BBC and MB I fear it really is a vision thing. No to dumbing down or we will all become dumb in both senses of the word.
Permian-Triassic
It was said that the most likely cause of the mass extinction was a huge increase in CO2, caused by volcanic action, this in turn (presumably) causing an intolerable rise in temperature. The result was that what had been a rainy climate, with marshy conditions, became hot and dry.If the temperature rose, then surely so would the rate of evaporation from the oceans. So what happened to all that suspended moisture? Clearly less of it fell on land as rain than had been the case during the cooler climate which preceded it - and I cannot believe that it all fell on the oceans!
Andrew - The Permian-Triassic Boundary
I was as fascinated by the contributors' descriptions of the lost world of the Permian and Pangaea as by the discussion of the possible ways by which it became lost.
Fred Kay Permian boundary
The participants established a credibleexplanation for the positive feedback global warming but I listened in vain for the reasons for it stabilising, at a high temperature, and any explanation of the recovery process. After all we do exist!
John Sears - rapid evolution
As a non-biologist I was surprised to learn how quickly a whole range of dynosaurs evolved - 20-30 million years - after the P-T mass extinction. An organism of any species is an extraordinarily complex system and I would have thought much longer time scales would be needed. It seems too quick a process to be driven by mutation and natural selection alone, unless perhaps small dynosaur prototypes had already developed. I wonder if we could have a programme on evolution which brings in ideas of gene swapping, gene editing and information transfers which appear to be happening in bacteria and could somehow be playing a role in plant and animal life.
Peter Solway - The Permian-Triassic Boundary
Throughout the programme I was hoping the parallels with current worst case projections for global warming might be discussed. Particularly, does the ability of the ecosphere to recover from the P-T event event, with its raising of the Earth's temperatures by 6 Deg C, suggest it is likely to recover (albeit over 50 million years) from the current event mankind is engineering ?
siberian traps
do we understand what caused the massive outpouring of volcanic lava in the Siberian area? is it not perfectly possible that this rupture of the earth's surface was actually caused by a massive meteor strike which was subsequently obscured by the lava flows which has covered the evidence of the strike? perhaps the meteor really did cause the problem after all. or do we have a more plausible explanation for the eruptions? can anybody tell
Ian Robinson - The Permian-Triassic Boundary
I listened with interest to this week's contributors and particularly Jane Francis' controversial contention that the mass extinction of 65 million years ago and, by implication the 250 million year 'event', was not the result of meteroritic activity. Mass Basal lava flows are now gaining credence as a probable cause. Has anyone considered the effects of a 'near' supernovae? Such a catastrophic explosion of a star in the Milky Way Galaxy would have sterilised all life on Earth and near planets such as Mars, which may have sustained a more fragile biosphere. Surviving species such as would be found at the bottom of the great ocean would have then evolved into species we see today. After 250 million years little forensic evidence would remain of the gamma radiation that would have bathed the Permian Earth.
jorg - in our time - 250ma
brill and easily understood. thankyou ALL the team. I look at the "Rock of ages", Burrington Combe, Somerset and can see the period that was talked about!?
Edward Crooks - Evolution of Animal Life on Earth
I have been interested in this subject since 1970 and in 1973 developed a theory that extinctions and subsequent revivals were caused by changes in the partial pressure of the two main biological gasses CO2 and O2, but mainly influenced by CO2. Reductions in CO2 pp and consequential increases in O2 pp have been responsible for the advances in metabolic rates from single cell animals in the Precambrian right through to the highest developed metabolic rates in modern animals alive today. That is because the animal can rid its tissue of more and more CO2 as the partial pressure of that gas reduces. On the other hand increases in CO2 have affected all animals to some extent. The highest metabolic rates along with animals with relatively large body masses would be the first to suffer if the partial pressure relationship between the two gasses moved in the wrong direction. Higher partial pressure of CO2 would force the retention of CO2 in animal tissue. The result would be a change in the pH value within the cell, this, in turn, would increase the instability of the genetic code with predictable results. The theory points to increasing numbers of individuals suffering from genetic disorders of all types because we are living in a period of increasing CO2 pp. In fact what the theory suggests is that there should be an observable increase in genetic disorders from that time in human development when CO2 pp decrease halted and began to increase. This, I think, would be about the beginning of the industrial revolution, or shortly after. It should be possible to use medical records to check if this is so. But an objection might be that certain substances have been identified as carcinogenic and these are what have caused the rise in some of the genetically related diseases because they have become increasingly common in the environment. My answer is; the increase in CO2 pp has made it more difficult for the cell to fight off the carcinogen thus allowing the disease to manifest itself more frequently that would otherwise be the case.I published this idea on the web in 1991 under the title, “The Evolution of the Atmosphere and its Effect on Animal Life”. This has not been updated since 1991 and includes descriptions of other effects the changes in the partial pressure of the two gasses has had on animal life.
|
|
