Stimate Domnule Ioan Toma,
Va dau totala dreptate in ceea ce citati, anume ca in timp, omul si cimpanzeul vor fi din ce in ce mai diferiti. Si completez inca odata, candva omul si cimpanzeul nu existau, exista doar un stramos comun al nostru.
Nu inteleg unde anume doriti sa ma contraziceti? Desigur, nu veti gasi ceva scris de mine, care sa fie in contradictie cu articolul postat de dvs. Niciodata nu ar putea afirma un biolog evolutionist o ineptie atat de mare, care sa sustina cum ca evolutia a ajuns la finalitatea ei, si o specie, sa zicem omul, nu mai continua sa se schimbe, sa evolueze...
Problema cu mesajul dvs este ca nu se intelege ce doriti sa demonstrati. Pentru mine, faptul ca evolutia biologica este un proces care continua, inclusiv la specia "om" este o chestiune evidenta.
Daca ati fi biolog, doctorand, cum sunt eu, ati fi
inteles de mult ca nu se pune problema ca toate "speciile", de la bacterii la om, sa nu se afle intr-o permanenta transformare, ca rezultat al 1. mutatiilor din materialul genetic, al 2. manifestarilor fenotipice ale schimbarilor genetice, si 3. a selectiei mediului in ceea ce priveste fenotipul, si implicit sansele lui de a lasa urmasi.
Desigur, evolutia poate fi mai lenta sau mai rapida, dar oricum se intampla. Evident, bacteriile sau organismele eucariote unicelulare sunt la un stadiu mai putin complex decat un palmier sau un papagal, ceea ce inseamna ca in ultimele miliarde de ani acele bacterii sau alge unicelulare nu au suferit atatea transformari majore, cate au avut liniile care au dus la existenta papagalilor sau palmierilor. Dar, cu toate acestea, pana si bacteriile "simple", prin uriasa lor viteza de a produce noi generatii (spre exemplu 20 de minute) se adapteaza foarte repede (spre exemplu) la antibiotice, si apar
astfel tulpini rezistente la acel antibiotic, o dovada a evolutiei care poate sa ne coste mult, atat la nivel de persoana cat si la nivel populational.
Desi am mentionat ceva tangential in mesajul precedent, desi incerc sa folosesc un limbaj cat mai simplu pentru a permite intelegerea ideilor de baza, poate ca totusi nu am fost destul de explicit, sa zicem cand am mentionat acele subspecii de la A-K, care partial se comporta ca apartinand unei specii, si partial se comporta ca specii diferite.... Desigur, toate acele subspecii/specii au un stramos comun, iar lentele sau rapidele acumulari de mutatii pot sa duca la diferentieri care sa le separe ca linii evolutive diferite.
In ceea ce il priveste pe dl Hortobagyi, l-am vazut intr-o emisiune televizata, nu stiu ce doreste, insa am considerat ca unele dintre afirmatiile domniei sale sunt interesante, si poate merita a fi cunoscute.
Cu prietenie,
:)
Peter Lengyel
PS. In ceea ce priveste celelalte afirmatii ale dvs., ele sunt foarte interesante, ca parte a diversitatii de opinii :)
"ioan.toma" <[EMAIL PROTECTED]> wrote:
Domnule Peter,
Ce ati scris dvs mai jos e doar interpretarea simplista, sa nu-i spunem copilareasca, a unor articole privite singular.Daca ati fi in domeniul genetic ar fi trebuit sa fi citit pina acum despre teoria conform careia omul se afla in continua evolutie.Deci daca cimpanzeul si omul au avut in general multe in comun, conform evolutiei continue careia se supun si omul si cimpanezul, ei vor deveni din ce in ce mai indepartati.
Cum se vede interpetarile dvs sint scolastice, banale si lipsite de cunostintele de baza in domeniul genetic si al biologiei.E si firesc sa fie asa dupa cum aglomerati toate cunostintele intr-un caleidoscop pseudo-stiintific sub Dumnezeul dvs Hardabagy Lazlo cel atoate stiutorul din care ne-ati citit ca dintr-o Biblie.
Acuma ca Hardabagy Lazlo asta ilustru anonim necunoscut poate nici pe ulita pe care s-a nascut, va place la nebunie am inteles noi dupa cum ni l-ati cintat mai ceva ca un popa calvinist.Numai ca n-am inteles de ce nu cititi si alceva.Va dau un exemplu aici si in ce priveste interpetarea religie-stiinta sint de acord ca un dobitoc pseudo-stiintific care se 'adapa' din reviste si ziare fara baza stiintifica necesara nu poate intelege substratul subiectului complex al religiei si tinde sa-l confunde cu masa pe care scrie pentru ca n-a ajuns sa gindesca nici macar la nivelul de elev de liceu care a intilnit notiunea de numar complex format din parte reala si parte imaginara.Prilej de prime intrebari pornind de la numere cum alta data au facut in alte conditii Pitagoreicii.Ca sa vedeti ca si 25 de secole in urma gindirea umana avea mai multe valente decit interpetarile dvs. anoste, insipide, inguste si unilaterale.
Still Evolving, Human Genes Tell New Story
http://www.nytimes.com/2006/ 03/07/science/ 07evolve. html?
_r=1&pagewanted=all&oref= slogin
Still Evolving, Human Genes Tell New Story
Peter Thompson for The New York TimesDr. Jonathan Pritchard writing
an equation to scan the human genome for signs of natural selection
Monday at the University of Chicago.
By NICHOLAS WADE
Published: March 7, 2006
Providing the strongest evidence yet that humans are still evolving,
researchers have detected some 700 regions of the human genome where
genes appear to have been reshaped by natural selection, a principal
force of evolution, within the last 5,000 to 15,000 years.
The genes that show this evolutionary change include some responsible
for the senses of taste and smell, digestion, bone structure, skin
color and brain function.
Many of these instances of selection may reflect the pressures that
came to bear as people abandoned their hunting and gathering way of
life for settlement and agriculture, a transition well under way in
Europe and East Asia some 5,000 years ago.
Under natural selection, beneficial genes become more common in a
population as their owners have more progeny.
Three populations were studied, Africans, East Asians and Europeans.
In each, a mostly different set of genes had been favored by natural
selection. The selected genes, which affect skin color, hair texture
and bone structure, may underlie the present-day differences in
racial appearance.
The study of selected genes may help reconstruct many crucial events
in the human past. It may also help physical anthropologists explain
why people over the world have such a variety of distinctive
appearances, even though their genes are on the whole similar, said
Dr. Spencer Wells, director of the Genographic Project of the
National Geographic Society.
The finding adds substantially to the evidence that human evolution
did not grind to a halt in the distant past, as is tacitly assumed by
many social scientists. Even evolutionary psychologists, who
interpret human behavior in terms of what the brain evolved to do,
hold that the work of natural selection in shaping the human mind was
completed in the pre-agricultural past, more than 10,000 years ago.
"There is ample evidence that selection has been a major driving
point in our evolution during the last 10,000 years, and there is no
reason to suppose that it has stopped," said Jonathan Pritchard, a
population geneticist at the University of Chicago who headed the
study.
Dr. Pritchard and his colleagues, Benjamin Voight, Sridhar
Kudaravalli and Xiaoquan Wen, report their findings in today's issue
of PLOS-Biology.
Their data is based on DNA changes in three populations gathered by
the HapMap project, which built on the decoding of the human genome
in 2003. The data, though collected to help identify variant genes
that contribute to disease, also give evidence of evolutionary change.
The fingerprints of natural selection in DNA are hard to recognize.
Just a handful of recently selected genes have previously been
identified, like those that confer resistance to malaria or the
ability to digest lactose in adulthood, an adaptation common in
Northern Europeans whose ancestors thrived on cattle milk.
But the authors of the HapMap study released last October found many
other regions where selection seemed to have occurred, as did an
analysis published in December by Robert K. Moysis of the University
of California, Irvine.
Dr. Pritchard's scan of the human genome differs from the previous
two because he has developed a statistical test to identify just
genes that have started to spread through populations in recent
millennia and have not yet become universal, as many advantageous
genes eventually do.
The selected genes he has detected fall into a handful of functional
categories, as might be expected if people were adapting to specific
changes in their environment. Some are genes involved in digesting
particular foods like the lactose-digesting gene common in Europeans.
Some are genes that mediate taste and smell as well as detoxify plant
poisons, perhaps signaling a shift in diet from wild foods to
domesticated plants and animals.
Dr. Pritchard estimates that the average point at which the selected
genes started to become more common under the pressure of natural
selection is 10,800 years ago in the African population and 6,600
years ago in the Asian and European populations.
Dr. Richard G. Klein, a paleoanthropologist at Stanford, said that it
was hard to correlate the specific gene changes in the three
populations with events in the archaeological record, but that the
timing and nature of the changes in the East Asians and Europeans
seemed compatible with the shift to agriculture. Rice farming became
widespread in China 6,000 to 7,000 years ago, and agriculture reached
Europe from the Near East around the same time.
Skeletons similar in form to modern Chinese are hard to find before
that period, Dr. Klein said, and there are few European skeletons
older than 10,000 years that look like modern Europeans.
That suggests that a change in bone structure occurred in the two
populations, perhaps in connection with the shift to agriculture. Dr.
Pritchard's team found that several genes associated with embryonic
development of the bones had been under selection in East Asians and
Europeans, and these could be another sign of the forager-to-farmer
transition, Dr. Klein said.
Dr. Wells, of the National Geographic Society, said Dr. Pritchard's
results were fascinating and would help anthropologists explain the
immense diversity of human populations even though their genes are
generally similar. The relative handful of selected genes that Dr.
Pritchard's study has pinpointed may hold the answer, he said,
adding, "Each gene has a story of some pressure we adapted to."
Dr. Wells is gathering DNA from across the globe to map in finer
detail the genetic variation brought to light by the HapMap project.
Dr. Pritchard's list of selected genes also includes five that affect
skin color. The selected versions of the genes occur solely in
Europeans and are presumably responsible for pale skin.
Anthropologists have generally assumed that the first modern humans
to arrive in Europe some 45,000 years ago had the dark skin of their
African origins, but soon acquired the paler skin needed to admit
sunlight for vitamin D synthesis.
The finding of five skin genes selected 6,600 years ago could imply
that Europeans acquired their pale skin much more recently. Or, the
selected genes may have been a reinforcement of a process established
earlier, Dr. Pritchard said.
The five genes show no sign of selective pressure in East Asians.
Because Chinese and Japanese are also pale, Dr. Pritchard said,
evolution must have accomplished the same goal in those populations
by working through different genes or by changing the same genes
but many thousands of years before, so that the signal of selection
is no longer visible to the new test.
Dr. Pritchard also detected selection at work in brain genes,
including a group known as microcephaly genes because, when
disrupted, they cause people to be born with unusually small brains.
Dr. Bruce Lahn, also of the University of Chicago, theorizes that
successive changes in the microcephaly genes may have enabled the
brain to enlarge in primate evolution, a process that may have
continued in the recent human past.
Last September, Dr. Lahn reported that one microcephaly gene had
recently changed in Europeans and another in Europeans and Asians. He
predicted that other brain genes would be found to have changed in
other populations.
Dr. Pritchard's test did not detect a signal of selection in Dr.
Lahn's two genes, but that may just reflect limitations of the test,
he and Dr. Lahn said. Dr. Pritchard found one microcephaly gene that
had been selected for in Africans and another in Europeans and East
Asians. Another brain gene, SNTG1, was under heavy selection in all
three populations.
"It seems like a really interesting gene, given our results, but
there doesn't seem to be that much known about exactly what it's
doing to the brain," Dr. Pritchard said.
Dr. Wells said that it was not surprising the brain had continued to
evolve along with other types of genes, but that nothing could be
inferred about the nature of the selective pressure until the
function of the selected genes was understood.
The four populations analyzed in the HapMap project are the Yoruba of
Nigeria, Han Chinese from Beijing, Japanese from Tokyo and a French
collection of Utah families of European descent. The populations are
assumed to be typical of sub-Saharan Africa, East Asia and Europe,
but the representation, though presumably good enough for medical
studies, may not be exact.
Dr. Pritchard's test for selection rests on the fact that an
advantageous mutation is inherited along with its gene and a large
block of DNA in which the gene sits. If the improved gene spreads
quickly, the DNA region that includes it will become less diverse
across a population because so many people now carry the same
sequence of DNA units at that location.
Dr. Pritchard's test measures the difference in DNA diversity between
those who carry a new gene and those who do not, and a significantly
lesser diversity is taken as a sign of selection. The difference
disappears when the improved gene has swept through the entire
population, as eventually happens, so the test picks up only new gene
variants on their way to becoming universal.
The selected genes turned out to be quite different from one racial
group to another. Dr. Pritchard's test identified 206 regions of the
genome that are under selection in the Yorubans, 185 regions in East
Asians and 188 in Europeans. The few overlaps between races concern
genes that could have been spread by migration or else be instances
of independent evolution, Dr. Pritchard said.
Parerea mea este ca stiinta si credinta sunt doua domenii totalmente diferite. Stiinta este rezultatul nu doar al "creatiei intelectuale" ci si al testarii teoriilor in practica. In stiinta, degeaba "crezi ceva", mai este nevoie si de date concrete care sa sustina "adevarul tau" in fata "parerii altora". In subdomeniul stiintific care se ocupa de studierea stiintifica a originii omului, nu este indeajuns sa se doreasca a se afirma ca omul provine din maimute, ci mai trebuie si "date ale experientei". Anatomie comparata, paleontologie, genetica, fiziologie comparata etc etc.
Eu personal, daca vad o gorila, si daca apoi ma uit la mine, in oglinda, nu prea vad diferente semnificative, atat de mari incat sa imi pun cat de cat serios problema ca am avea o origine filogenetica diferita, atat de diferita incat acela sa fie animal, iar eu o creatie a unei divinitati care m-a facut pe chipul si asemanarea sa.
Daca imi numar degetele, daca ma uit la unghii, la dispunerea si diferentierea dentitiei, la oase, de la vertebre la falange si la cele care imi compun craniul, nu vad decat o diferenta de detalii nesemnificative. Daca ma uit la globulele din sange, la lobii pulmonari, la structura inimii sau a rinichilor, la lobii encefalului, la structura pielii si a firelor de par, la ochi si la iris, la stomac si la duoden, la glandele endocrine si la puiul alaptat la san, nu vad decat diferente de detalii. Orice as analiza, nu vad decat diferente de detalii.
Materialul genetic uman se suprapune peste 99% cu cel al maimutelor antropoide, ceea ce cred ca trebuie sa dea de gandit oricarui bigot. Faptul ca speciile inrudite apropiat pot avea un numar diferit de cromosomi, este desigur "la mintea cocosului". Chiar si specii din acelasi gen, au cariotipuri diferite, rearanjari ale materialului genetic in cadrul cromosomilor, etc, aceste deosebiri ale detaliilor fiind parte a diferentelor dintre "specii". Desigur, un biolog care intelege cat de cat evolutia, stie ca pana si termenul de "specie" este o "realitate virtuala", o incercare a omului de "a pune in ordine" ceea ce vede in jurul sau. In realitate "speciile" sunt fragmentate in subspecii sau "rase locale", mai mult sau mai putin inrudite intre ele, unele putand avea urmasi fertili intre ele, altele avand grade crescute de incompatibilitate genetica, pana la comportarea ca specii diferite. Spre exemplu, daca o "specie?" are populatiile A, B, C, D, E, F, G, H, I, J, K, asezate sub forma de semicerc, sa zicem pe niste insule, iar A si B produc urmasi fertili, la fel, B cu C si asa mai departe, insa A si K, daca ajung impreuna (sa zicem ca "cercul se inchide"), prezinta diferente atat de mari, incat se comporta ca "specii" diferite... Ma intreb atunci, ce este in cazul de fata, o specie, doua, si unde anume este limita intre ele? Desigur, vedem ca termenul in sine este o chestiune necesara noua pentru a putea "ordona natura" in cartile simple de biologie, sau pentru colectionarii de timbre...
Daca avem curiozitatea naturala, "sa nu ramanem nestiutori de carte stiintifica", si ajungem macar sa citim presa la nivel de jurnale credibile, sa vedem spre exemplu un articol din Washington Post, din 18 mai 2006, putem vedea ca data de despartire a cimpanzeului de om este estimata, pe baze genetice (precum si pe baze fosile) la circa 6,3 milioane de ani in urma, dar pare ca 'cimpanzeii' si 'oamenii' se mai distrau impreuna pana in urma cu circa 1,2 milioane de ani in urma, cand separatia a fost mai profunda. Deci, unde este acea urisa diferenta, ca am veni din locuri diferite?
http://www.washingtonpost.com/ wp-dyn/content/ article/2006/ 05/17/AR20060517 02158.html
Ori daca citim articolul de la la:
http://www.uchicago.edu/aff/ mwc-amacad/ biocomplexity/ conference_ papers/goodman. pdf#search= %22human% 20monkey% 20genetics% 22
putem vedea ca ADNul functional al omului si al cimpanzeilor arata ca ei sunt mai asemanatori unul fata de celalalt, decat este oricare dintre ei fata de alte specii de maimute antropide.
Dar, desigur aceste chestii nu au nici o valoare atat timp cat traiesti in sfera "crede si nu cerceta", cat timp in scoala, de mic copil esti indoctrinat ca un dobitoc de preoti care "stiu Adevarul", si cat timp ai "dorinte sexuale permanente".
Cu prietenie,
:)
Peter Lengyel
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