quote:When Charles Darwin published The Origin of Species 150 years ago he consciously avoided discussing the origin of life. However, analysis of some other texts written by Darwin, and of the correspondence he exchanged with friends and colleagues demonstrates that he took for granted the possibility of a natural emergence of the first life forms. As shown by notes from the pages he excised from his private notebooks, as early as 1837 Darwin was convinced that “the intimate relation of Life with laws of chemical combination, & the universality of latter render spontaneous generation not improbable”.
Like many of his contemporaries, Darwin rejected the idea that putrefaction of preexisting organic compounds could lead to the appearance of organisms. Although he favored the possibility that life could appear by natural processes from simple inorganic compounds, his reluctance to discuss the issue resulted from his recognition that at the time it was impossible to undertake the experimental study of the emergence of life.
De rest op NU.nlquote:Hyena's met een hoge sociale status leven vermoedelijk bovengemiddeld lang. Dat zou blijken uit nieuw wetenschappelijk onderzoek.
Als hyena's hoog in de hiërarchie van hun roedel staan, zijn hun telomeren gemiddeld genomen langer dan die van hun soortgenoten .
Dat melden onderzoekers van Michigan State University in het wetenschappelijk tijdschrift Current Biology.
Telomeren zijn de uiteinden van chromosomen. De stukjes DNA bepalen hoe vaak een cel zich deelt en hebben waarschijnlijk grote invloed op de gezondheid en levensduur van dieren.
quote:Abstract
Telomeres are regarded as important biomarkers of ageing and serve as useful tools in revealing how stress acts at the cellular level. However, the effects of social and ecological factors on telomere length remain poorly understood, particularly in free-ranging mammals. Here, we investigated the influences of within-group dominance rank and group membership on telomere length in wild adult spotted hyenas (Crocuta crocuta). We found large effects of both factors; high-ranking hyenas exhibited significantly greater mean telomere length than did subordinate animals, and group membership significantly predicted mean telomere length within high-ranking females. We further inquired whether prey availability mediates the observed effect of group membership on telomere length, but this hypothesis was not supported. Interestingly, adult telomere length was not predicted by age. Our work shows for the first time, to the best of our knowledge, the effects of social rank on telomere length in a wild mammal and enhances our understanding of how social and ecological variables may contribute to organismal senescence.
University of Floridaquote:Two most destructive termite species forming superswarms in South Florida, UF study finds
Two of the most destructive termite species in the world -- responsible for much of the $40 billion in economic loss caused by termites annually -- are now swarming simultaneously in South Florida, creating hybrid colonies that grow quickly and have the potential to migrate to other states.
[...]
UF scientists previously thought the two termite species had distinct swarming seasons that prevented them from interacting. Their new research indicates not only an overlap of seasons where the two species are interbreeding; it shows that male Asian termites prefer to mate with Formosan females rather than females of their own species, increasing the risk of hybridization.
quote:Oldest stone tools pre-date earliest humans
They were unearthed from the shores of Lake Turkana in Kenya, and date to 3.3 million years ago.
They are 700,000 years older than any tools found before, even pre-dating the earliest humans in the Homo genus.
The find, reported in Nature, suggests that more ancient species, such as Australopithecus afarensis or Kenyanthropus platyops, may have been more sophisticated than was thought.
"They are significantly earlier than anything that has been found previously," said Dr Nick Taylor, from the National Centre of Scientific Research (CNRS) in France and the University of Leiden in the Netherlands.
"It's really quite astonishing to think what separates the previous oldest site and this site is 700,000 years of time. It's monumental."
Creativity in evolutie? Het is toch geen Intelligent Design!quote:Op zondag 23 augustus 2015 22:23 schreef Molurus het volgende:
Computer scientists find mass extinctions can accelerate evolution
... the research supports the idea that mass extinctions actually speed up evolution by unleashing new creativity in adaptations.
[ afbeelding ]
Bron: Science Daily.
Dat soort beeldspraak is bijna onvermijdelijk. Toch neem ik aan dat je begrijpt dat men het niet heeft over ontwerp maar de schijn van ontwerp alsmede de schijn van creativiteit.quote:Op zondag 23 augustus 2015 23:27 schreef Broomer het volgende:
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Creativity in evolutie? Het is toch geen Intelligent Design!
Ik vind het altijd een beetje tenenkrommend, die beeldspraak. Helpt ook niet om een beter begrip bij de leek bij te brengen. Die denkt nog steeds dat evolutie iets gestuurd is, met de mens als (voorlopig) hoogtepunt.quote:Op zondag 23 augustus 2015 23:31 schreef Molurus het volgende:
[..]
Dat soort beeldspraak is bijna onvermijdelijk. Toch neem ik aan dat je begrijpt dat men het niet heeft over ontwerp maar de schijn van ontwerp alsmede de schijn van creativiteit.
Het gaat over de snelheid waarmee nieuwe aanpassingen zich vormen. Het lijkt erop dat massa extincties de snelheid van evolutie verhogen. En dat is toch een tamelijk opmerkelijke bevinding.
"Adaptatie" is in deze context al een beeldspraak. Wellicht zouden we moeten spreken van "een verandering die gunstig uitwerkt". Maar het wordt dan wel heel krampachtig taalgebruik.quote:Op maandag 24 augustus 2015 06:14 schreef Broomer het volgende:
[..]
Het is toch ook niet echt nodig? Je kan toch ook "onverwachte adaptaties", of "geheel nieuwe adaptaties", of zoiets zeggen?
quote:Study of Holocaust survivors finds trauma passed on to children's genes | Science | The Guardian
New finding is first example in humans of the theory of epigenetic inheritance: the idea that environmental factors can affect the genes of your children
Genetic changes stemming from the trauma suffered by Holocaust survivors are capable of being passed on to their children, the clearest sign yet that one person’s life experience can affect subsequent generations.
The conclusion from a research team at New York’s Mount Sinai hospital led by Rachel Yehuda stems from the genetic study of 32 Jewish men and women who had either been interned in a Nazi concentration camp, witnessed or experienced torture or who had had to hide during the second world war.
They also analysed the genes of their children, who are known to have increased likelihood of stress disorders, and compared the results with Jewish families who were living outside of Europe during the war. “The gene changes in the children could only be attributed to Holocaust exposure in the parents,” said Yehuda.
Related: Holocaust survivors' grandchildren call for action over inherited trauma
Her team’s work is the clearest example in humans of the transmission of trauma to a child via what is called “epigenetic inheritance” - the idea that environmental influences such as smoking, diet and stress can affect the genes of your children and possibly even grandchildren.
The idea is controversial, as scientific convention states that genes contained in DNA are the only way to transmit biological information between generations. However, our genes are modified by the environment all the time, through chemical tags that attach themselves to our DNA, switching genes on and off. Recent studies suggest that some of these tags might somehow be passed through generations, meaning our environment could have and impact on our children’s health.
Other studies have proposed a more tentative connection between one generation’s experience and the next. For example, girls born to Dutch women who were pregnant during a severe famine at the end of the second world war had an above-average risk of developing schizophrenia. Likewise, another study has showed that men who smoked before puberty fathered heavier sons than those who smoked after.
The team were specifically interested in one region of a gene associated with the regulation of stress hormones, which is known to be affected by trauma. “It makes sense to look at this gene,” said Yehuda. “If there’s a transmitted effect of trauma, it would be in a stress-related gene that shapes the way we cope with our environment.”
They found epigenetic tags on the very same part of this gene in both the Holocaust survivors and their offspring, the same correlation was not found in any of the control group and their children.
Through further genetic analysis, the team ruled out the possibility that the epigenetic changes were a result of trauma that the children had experienced themselves.
“To our knowledge, this provides the first demonstration of transmission of pre-conception stress effects resulting in epigenetic changes in both the exposed parents and their offspring in humans,” said Yehuda, whose work was published in Biological Psychiatry.
It’s still not clear how these tags might be passed from parent to child. Genetic information in sperm and eggs is not supposed to be affected by the environment - any epigenetic tags on DNA had been thought to be wiped clean soon after fertilisation occurs.
However, research by Azim Surani at Cambridge University and colleagues, has recently shown that some epigenetic tags escape the cleaning process at fertilisation, slipping through the net. It’s not clear whether the gene changes found in the study would permanently affect the children’s health, nor do the results upend any of our theories of evolution.
Whether the gene in question is switched on or off could have a tremendous impact on how much stress hormone is made and how we cope with stress, said Yehuda. “It’s a lot to wrap our heads around. It’s certainly an opportunity to learn a lot of important things about how we adapt to our environment and how we might pass on environmental resilience.”
The impact of Holocaust survival on the next generation has been investigated for years - the challenge has been to show intergenerational effects are not just transmitted by social influences from the parents or regular genetic inheritance, said Marcus Pembrey, emeritus professor of paediatric genetics at University College London.
“Yehuda’s paper makes some useful progress. What we’re getting here is the very beginnings of a understanding of how one generation responds to the experiences of the previous generation. It’s fine-tuning the way your genes respond to the world.”
Researchers have already shown that certain fears might be inherited through generations, at least in animals.
Scientists at Emory University in Atlanta trained male mice to fear the smell of cherry blossom by pairing the smell with a small electric shock. Eventually the mice shuddered at the smell even when it was delivered on its own.
Despite never having encountered the smell of cherry blossom, the offspring of these mice had the same fearful response to the smell - shuddering when they came in contact with it. So too did some of their own offspring.
On the other hand, offspring of mice that had been conditioned to fear another smell, or mice who’d had no such conditioning had no fear of cherry blossom.
The fearful mice produced sperm which had fewer epigenetic tags on the gene responsible for producing receptors that sense cherry blossom. The pups themselves had an increased number of cherry blossom smell receptors in their brain, although how this led to them associating the smell with fear is still a mystery.
Bron: www.theguardian.com
Design staat echt voor een bewuste actie, dus een plan maken voor iets. De natuur vormt het leven wel, maar ontwerpt het niet.quote:Op zondag 30 augustus 2015 02:29 schreef NobodyKerz het volgende:
Ik vind design wel goed passen bij evolutie. De natuur is immers de designer.
Ligt er maar net aan hoe je design wil zien. De definitie die ik en sommige anderen gebruiken zijn ook toepasbaar op bijvoorbeeld zwaartekracht; zwaartekracht designed de vorm van de planeten en ons zonnestelsel.quote:Op zondag 30 augustus 2015 02:36 schreef Stompzinnig het volgende:
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Design staat echt voor een bewuste actie, dus een plan maken voor iets. De natuur vormt het leven wel, maar ontwerpt het niet.
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