High Energy Cosmic Rays and the Origin of Life
|Sep12-12, 08:59 AM||#1|
High Energy Cosmic Rays and the Origin of Life
The advocators of Darwinís theory of evolution discover that it is difficult for normal evolution rate alone to form the species diversity now. What factor(s) accelerated the origin of life and species diversity?
Novae, especially supernovae, would generate high energy cosmic rays that would impact on acceleration of creature DNA gene mutation during this period, thus create lots of new species.
The best supernova rate estimate we can offer indicates that one or more supernova explosions are likely to have occurred within 10 pc or so of the Earth during the Phanerozoic era, i.e., during the last 570 million years since the sudden biological diversification at the start of the Cambrian. (CERN)
CERN-TH.6805/93, John Ellis et al.
|Sep12-12, 10:03 AM||#2|
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For a start there is no "normal evolution rate", species can remain stable for millions of years whilst others can speciate in decades. In addition the biodiversity of Earth has risen and fallen multiple times accross it's long history.
|Sep12-12, 12:32 PM||#3|
High energy cosmic rays can cause an increase in UV radiation. However, UV radiation does not cause mutation in large organisms. The high energy cosmic radiation could itself cause mutation in large organisms. I conjecture that you are referring to mutations caused by high energy cosmic rays on large animals. However, high energy cosmic rays that hit the ground would have left a large amount of radioactive contamination.
The changes in the rate of evolution are not usually caused by changes in mutation rate. Changes in the rate of speciation can be caused by a change in the environment. The punctuations in the evolutionary record seem correlated more with catastrophes then with radiations.
According to the punctuated theory, sudden catastrophes of any type can cause a discontinuity in the fossil record by causing the extinction of species. The extinction of common species allows rare species to multiply. They take over the ranges of the common species. The mutation rate does not have to change. The development of new species can occur on a much longer time scale.
“Transitional forms are generally lacking at the species level, but they are abundant between larger groups." Although there exist some debate over how long the punctuations last, supporters of punctuated equilibrium generally place the figure between 50,000 and 100,000 years.”
A supernova would not cause a flux of radiation that would last 50 KY. It would be more like decade, or maybe a few decades. The pattern of mutations caused by an influx of radiation would cause gene deletions that would be apparent even in extant organisms.
Radiation tends to cause point mutations that delete a gene. Thus, a sudden influx of radiation would result in a sudden decrease of genes. Most of those deletions would result in a saltation, which would be immediately eliminated. There would be differences in the sizes of the genome that would appear in closely related species. That does not appear to happen. There are few cases of gene deletion in the genomes of extant organisms.
“Two classes of mutations are spontaneous mutations (molecular decay) and induced mutations caused by mutagens.
<Big list of causes of mutation.>
Two nucleotide bases in DNA – cytosine and thymine – are most vulnerable to radiation that can change their properties. UV light can induce adjacent pyrimidine bases in a DNA strand to become covalently joined as a pyrimidine dimer. UV radiation, particularly longer-wave UVA, can also cause oxidative damage to DNA.”
I don’t know how common pyrimidine dimes are in the genomes of modern organisms. However, I haven’t found much in the literature on these mutations. Radiation producing mutations sounds like an easily reproduced experiment in the laboratory, but it doesn’t appear to have left much of a record in nature. Of course, there are other causes of mutation that have left a larger record in the genomes of extant organisms.
<Bigger list of causes of mutation.>
In order to form a new species, there has to be a large series of mutations that have very small effects. Saltations are preferentially lethal, as opposed to beneficial. However, small changes have a significant chance of being beneficial. Deleting a gene tends to cause saltations. If a regulatory gene is deleted by the radiation, there may be smaller mutations. However, the effect of a series of such mutations would be a smaller genome. There are other mechanisms for mutation that would not decrease the number of genes. These are more likely involved in evolution.
“Saltation does not fit into contemporary evolutionary theory, but there are some prominent proponents, including Carl Woese. Woese, and colleagues, suggested that the absence of RNA signature continuum between domains of bacteria, archaea, and eukarya constitutes a primary indication that the three primary organismal lineages materialized via one or more major evolutionary saltations from some universal ancestral state involving dramatic change in cellular organization that was significant early in the evolution of life, but in complex organisms gave way to the generally accepted Darwinian mechanisms. “
Obviously, the mutation caused by supernovas aren’t necessary to explain speciation in all cases. However, supernovas can trigger rapid speciation events by changing the environment. For example, the end-Ordovician mass extinction may have been caused by a supernova. If so, the mutation rate wasn’t the driving factor for the rapidity of the speciation. The extinction of large numbers of organisms caused a change in the environment that started organisms evolving. However, there is no evidence that the rate of speciation increased.
I present end-Ordovician extinction as the exception that proves the rule. The supernova event in this case, if it happened at all, did more killing than mutating.
“A nearby gamma ray burst (less than 6000 light years away) would be powerful enough to destroy the Earth's ozone layer, leaving organisms vulnerable to ultraviolet radiation from the sun. Gamma ray bursts are fairly rare, occurring only a few times in a given galaxy per million years. It has been suggested that a supernova or gamma ray burst caused the End-Ordovician extinction. ”
Please note that UV radiation can only cause mutations in transparent organisms that live near or above the surface of the water. For example, UV radiation can’t penetrate animal skin so it can’t reach the gametes. UV radiation shining on animals can only cause sunburn and cancer. UV can’t cause mutation in animals.
The increase in UV radiation could only kill large animals and plants. Any increase in the rate of evolution caused by UV radiation would be primarily caused by extinction, not mutation. Extinctions change the environment.
There are many cases of rapid speciation that have been studied in the field. However, none of these cases have involved a flux of radiation. In each case observed, the speciation event was triggered by a change in environment. The mutations involved were extremely small. There was no increase in the number of genes deleted in their genome. The mechanisms of these mutations are still unknown, but the changes in environment are very well documented. Therefore, scientists tend to classify different types of speciation in terms of changes in environment.
“There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, parapatric, and sympatric. Speciation may also be induced artificially, through animal husbandry, agriculture, or laboratory experiments. Observed examples of each kind of speciation are provided throughout.”
Here is a field study example of a speciation event that happened rapidly with no radiation. There are a few such events, but this is a really interesting one.
Rhagoletis pomonella is a case of rapid speciation that did not involve radiation. The apple maggot differentiated into a hawthorne maggot and a blueberry maggot a time interval that was only a few decades long. There was no supernova event correlated with this speciation.
"Rhagoletis pomonella is significant evolutionarily in that the race of this species that feeds on apples spontaneously emerged from the hawthorn feeding race in the 1800 - 1850 CE time frame after apples were introduced into North America. The apple feeding race does not now normally feed on hawthorns and the hawthorn feeding race does not now normally feed on apples. This constitutes a possible example of an early step towards the emergence of a new species, a case of sympatric speciation.
The emergence of the apple race of Rhagoletis pomonella also appears to have driven formation of new races among its parasites."
There is no supernova recorded in the 1800-1850 time span. In fact, there was no change in the number of sunspots either. There is no evidence that the radiation illuminating the earth changed at all in the 1800-1850 time span. Rhagoletis came to the land of opportunity and literally branched out. So did its waspish parasites.
So the theory of evolution doesn't need supernovas to be consistent with the data. Evolution usually occurs without supernovas by mechanisms that are fairly well known.
|Sep12-12, 02:32 PM||#4|
High Energy Cosmic Rays and the Origin of Life
It may be useful to consider the exception that proves the role. The end-Ordovician extinction may have been caused by a nearby supernova. Most scientists don’t think so. However, a small minority of scientists are considering the idea that maybe a supernova may have caused it. However, you may find it interesting why this minority is considering the idea that a supernova caused it.
Please note that there were no land animals or land plants until the Silurian. Land animals continued to develop for millions of years after the end-Ordovician event. So when I say that there was selectivity in the extinction of sea animals at the end of the Ordovician, I am saying that there is selectivity in the extinction of all animals.
The extinctions that occur at the end of the Ordovician are rather selective. Most of the organisms that died off were microscopic, such that UV could have shined through them. Some of the larger animals that died off were those that lived on the surface of the ocean. The large animals that did not die off were those that lived deep underwater.
The trilobites are a class of arthropods that are particularly good examples. For instance, the trilobites that died off lived near the surface of the water. Trilobites that lived deep underwater did not die off. Since the anatomy of trilobites is somewhat similar, the differential extinction is hypothesized to be caused by an environmental cause. However, this can’t be cause by the mutation of trilobites since trilobites are too big to allow UV radiation through their bodies. The UV radiation could cause their deaths my irradiating cells on their surface. It could not have increased their mutation rate. If evolution was caused by the larger mutation rate, then the trilobites on the surface would have differentiated rather than go extinct. So I conclude that neither UV nor cosmic ray radiation caused mutation in trilobites.
Furthermore, there is a latitudinal variation in extinction rates that is not consistent with the other catastrophes occurring at that time. It is for the reason of this selectivity that some scientists are considering the supernova hypothesis.
Note that other extinctions do not show this type of selectivity. There are at least four other extinctions of comparable extent, and none of them show this pattern. Furthermore, there is speciation and evolution over the entire Phanerozoic era. As your reference points out, the likelihood is small that there were a large number of nearby supernovas during this time. To produce the constant turnover of species in the Phanerozoic era, there must have been a constant battery of nearby supernova events.
So the influence of a supernova at best can explain the initial stages of the end-Ordovician extinction. Supernovas can't explain the rest of evolution.
Here are two links on the end-Ordovician extinction.
At the time, most complex multicellular organisms lived in the sea, and around 100 marine families became extinct, covering about 49% of faunal genera (a more reliable estimate than species). The brachiopods and bryozoans were decimated, along with many of the trilobite, conodont and graptolite families.
Statistical analysis of marine losses at this time suggests that the decrease in diversity was mainly caused by a sharp increase in extinctions, rather than a decrease in speciation.
These extinctions are currently being intensively studied. The pulses appear to correspond to the beginning and end of the most severe ice age of the Phanerozoic, which marked the end of a longer cooling trend in the Hirnantian faunal stage towards the end of the Ordovician, which had more typically experienced greenhouse conditions.
The event was preceded by a fall in atmospheric CO2, which selectively affected the shallow seas where most organisms lived. As the southern supercontinent Gondwana drifted over the South Pole, ice caps formed on it.
A small minority of scientists have suggested that the initial extinctions could have been caused by a gamma ray burst originating from a hypernova within 6,000 light years of Earth (in a nearby arm of the Milky Way Galaxy). A ten-second burst would have stripped the Earth's atmosphere of half of its ozone almost immediately, exposing surface-dwelling organisms, including those responsible for planetary photosynthesis, to high levels of ultraviolet radiation.  Although the hypothesis is consistent with patterns at the onset of extinction, there is no unambiguous evidence that such a nearby gamma ray burst ever happened.”
Based on the intensity and rates of various kinds of intense ionizing radiation events such as supernovae and gamma-ray bursts, it is likely that the Earth has been subjected to one or more events of potential mass extinction level intensity during the Phanerozoic. These induce changes in atmospheric chemistry so that the level of Solar ultraviolet-B radiation reaching the surface and near-surface waters may be approximately doubled for up to one decade.
We previously proposed that the late Ordovician extinction is a plausible candidate for a contribution from an ionizing radiation event, based on environmental selectivity in trilobites.”
|cosmic ray, origin of life, origin of species|
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