This is a frozen archive of the debate I moved from the Hensel Twins post due to length.
EVOLUTIONIST (xeno): I see the [Hensel] twins as an example that evolution is taking place all around us, right now, as it has for billions of years. They are living proof that major changes in our biology occasionally happen. If the genetic anomaly which kept them from separating was passed on to their own offspring, we could have a new population of joined people. If they preferred their own kind over time and changed enough so that they no longer mated with the one-headers, then at that point, their ancestors would be a new species.
REBUTTAL (ssleb): not exactly.. siamese twins are not the result of genetics, they are the result of developmental errors in the early stages of pregnancy.
EVOLUTIONIST (xeno): The creation of a new person is an intricate dance, but genetics are involved. I believe that a mutation in the parent which triggers another mutation to happen during cell division and which is also passed on to the offspring could lead to the trait of conjoined twins being passed on. Unlikely, but not impossible, especially over millions of years.
I’m basing this on the idea that ordinary identical twins happen when a mutation at an early stage causes a dividing cell to reject part of itself as “other” and then the two cell lines continue to develop separately. This is supported by observed “identical” twins which have different genetic traits. Since the developing twins are “almost identical” cell lines, they may, at random, bump and rejoin at different stages.
I don’t know for a fact that a genetic mutation could cause a division error that leads to a mutation in just one of replicated pairs… but I don’t see why that would be impossible.
COMMENT: (pharaphrased:) It is rude to say the twins are a new species.
EVOLUTIONIST (xeno): I was pointing out the biological mechanism by which new species arise.
The fact is, like them, we are all the result of multiple individual organisms fusing over time.
Consider our mitochondria. These are cell parts we all have. which were once bacteria. Evolutionarily they became part of the animals which eventually became us. Our mitochondria even today still have their own DNA.
It annoys some people, and it frightens others, but from a science perspective we are not pure perfect human creations of God which happened instantly. We are intricate messy groups of cells which found ways to survive together as entities over billions of years of random experimentation.
The endosymbiotic relationship of mitochondria with their host cells was popularized by Lynn Margulis. The endosymbiotic hypothesis suggests that mitochondria descended from bacteria that somehow survived endocytosis by another cell, and became incorporated into the cytoplasm. The ability of these bacteria to conduct respiration in host cells that had relied on glycolysis and fermentation would have provided a considerable evolutionary advantage. In a similar manner, host cells with symbiotic bacteria capable of photosynthesis would also have had an advantage. The incorporation of symbiotes would have increased the number of environments in which the cells could survive. This symbiotic relationship probably developed 1.7 -2 billion years ago. – wiki
REBUTTAL (ticktick): the twins could not be a “new species” because identical twins themselves are a fluke. it is genetic to have fraternal twins. get your facts before you make some radical rediculous statement like that.
EVOLUTIONIST: I did not say the twins are or could be a new species. I said that they are an example that very different configurations of human biology can sometimes exist. This is part of how different species get created. Over huge spans of times, occasionally some differences get passed on genetically and one species can split into multiple species. Various splits in the past of one species splitting is why we look most similar to apes, kind of similar horses, only slightly similar to birds, and very unlike trees.
Most people have no clue about how the different species we have today came to exist.
REBUTTAL (jaima) xeno, you’re an idiot. conjoined twins are just the result of the fertilized egg failing to completely separate. it’s not a genetic trait, they could never become a new species. and the fusion of organisms is only a plausible theory at the most primitive level of life.
EVOLUTIONIST (xeno): Jaima, Genes govern all stages of reproduction. I’m saying an inheritable genetic defect can cause fertilized eggs to fail to separate. The twins themselves could not become a new species, obviously. But over time, their unique condition could be passed on if it were due to a genetic mutation which altered the process of early development. Over time, this could lead to a new species. Fusion of organisms does not drive species creation. I point out only that very different configurations of our biology can sometimes happen and that when these changes have a genetic basis, they get passed on.
The actual genetic change which might be responsible may exist in the twin’s mother because messenger RNA from the mother controls the early part of the dance.
This is because in the egg, there exists a stockpile of maternally derived mRNAs which govern embryogenesis through cleavage to the blastula stage. Following the formation of the blastula, zygotic gene transcription is activated, which carries the embryo through the rest of embryogenesis. – link
Although RNA in sperm may do more than is currently understood.
REBUTTAL (ANON) : Xeno, you are a cad. And yes, Scientific theory though it MAY seem, The truth is that you Xeno are full of Psychobabble, most likely having delved only deep enough into your studies to confound and “impress” others with your ill reserved banter. Evolutionist Pig. How Dare you suggest that the complexity and “chance” which constructs organisms rule out the chance of a higher being? THAT my friends is ignorance.
REBUTTAL (gaby): I disagree with Xeno’s “theory” that these girls are the progenitors of some new ‘species.’ Their DNA would be that of Homo Sapiens just like the rest of us humans. Their offspring would also be Human. Humans are the only extant species of the primate family Hominidae. In addition, the defect of conjoining is not confined to man. It occurs in many other species. The proverbial ‘two headed calf’ was a big draw at traveling carnivals and side shows in the 1900’s and early in the 20th Century. I do not believe there is a genetic defect that can even be passed on from a conjoined twin to its offspring that would lead to that offspring also producing conjoined twins.
In regard to the male-female conjoined twins- there is no way for that to occur. In the case you sited you left out the rest of the story. Which is: “It is suspected that pseudohermaphroditism, a condition where external genitals resemble that of the opposite sex, exists in one of the twins.”
While genetic abberations do occur all the time, Abby and Brittany simply have a condition related to some malfunction in the way the cells divided after the egg was fertilized. We don’t need to call in Mulder and Scully!
EVOLUTIONIST (xeno): Gabby, great apes, chips, gorillas and orangutans all do exist. All of us are members of the biological family Hominidae. Different species, same family. I did not say that a genetic defect WILL be passed on, but if that DID happen, and if over time a two headed group only mated with itself, and in time due to other genetic changes if the two headed group became unable to mate with the one headed group, then at that point you would have two different species. (A species, by definition, is a group that can only mate with itself and produce fertile offspring.)
Evolution is why we have different species in our family. I’m astonished, really, that anyone could look at (chimps, apes, us, and gorillas), and then at (horses, zebras, donkeys), and not realize that there are different groupings of animals with similar traits.
Why would that be? The answer: evolution. Common ancestors result in similar traits. Or perhaps you believe God lacked the creativity to make every creature completely unique?
Anon, look up psychobabble and you won’t see the terms like mRNA, embryogenesis, blastula, or monozygotic. What’s your beef, anyway? You don’t believe mRNA exists? You don’t believe it controls early embryogenesis? You don’t believe mRNA damage could result in conjoined twins? Remember, your computer, car, TV, cell phone, and radio each resulted from the same scientific method which gives us evolution.
Our understanding of evolution results from observing the physical world: fossils, genetics, geology, etc. Cynognathus, for example, were real animals which were an evolutionary step between reptiles and mammals. Evolution happened. The reason you don’t see many more transitional species is that the conditions to make fossils happen very rarely. Most creatures that have died have completely vanished through decomposition. All parts of dead animals, even teeth and bones, normally break down or are scattered by scavengers.
Higher beings? When did I rule out aliens? I didn’t.
No one said the twins are a new species. Read this.
READ Evolution / Creation Debate (Part 2)