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Note: This blog does not express the author's opinion on the possibility of cloning dinosaurs. It simply shows a more skeptical view towards it.
DNA in amber
- Just because the Cretaceous weevil DNA was similar but still distant from modern weevil DNA does not imply that the DNA was endogenous. It is important to remember that there are many species of beetles, and many have not had DNA sequenced from them yet. It is possible that future BLAST searches will reveal the DNA to be contaminated from modern beetles. Many scientists believe that Cano's lab didn't have proper sterlization. While it is impossible to know for certain without watching the extraction, the scientists can see pictures and even go to Cano's lab to see for themselves. A more important note is that Poinar didn't send the amber sample to the lab, but instead sent a tissue sample he got from the beetle, meaning that it could have been contaminated with just about anything on the way. If one wants to extract DNA from amber insects, it would be a lot wiser to send the insects when they are still in the fossil resin.
DNA in bones
- MismeretMonk seems to believe that the DNA that Schweitzer found in dinosaur bone cells cannot be contamination because the DNA only binded to the cores of the cells, just like ostrich cells. This indeed debunks microbial and fungal contamination, and makes human contamination unlikely, but it is impossible to know without sequence data. Just because a study hasn't been disproven does not mean that it isn't wrong. Saying otherwise is a pretty good way to become a pseudoscientist, which includes people such as creationists, Singularity believers and the Flat Earth Society.
- Many critics point at out if it was possible to get DNA from dinosaur bones, many such studies would have been done today. While scientific bias exists, these people indeed have a point. I was personally surprised that absolutely NO work had been published work about dinosaur DNA in bones, apart from Schweitzer's recent paper and many supposed reports that turned out to be sample contamination.
- Ancient gene prediction has been criticized by several scientists. They contend that methods such as maximum likelihood may produce very inaccurate results. I don't think this explains why the Triassic archosaur gene was functional, though.
- Certain scientists have tried to reconstruct proteins even more ancient than the dinosaurs, only to find out that such sequences were no longer functional. While this may be due to evolution and prediction errors, it may put reports of success to question.
Filling in the sequence gaps
- It is true that genes are conserved throughout evolution. However, as Ryan Whitwam noted on extremetech.com, a single wrong base pair can make a gene non-functional. It is possible to test genes, but if a gene turns out to be non-functional, it may take a lot of hard work to get the gene right.
- Any regulatory DNA in fossils and amber will be short fragments. Using a wide variety of specimens, it may only be possible to create a few complete ancient regulatory sequences at the most. We can also design regulators on a computer, but it may take many more years of research.
- While the chicken and houbara bustard belong to different orders, this is still different from making a raptor-ostrich chimera. Many other classification levels exist between them, such as infraorders and superorders. I don't know much about classification with either Linnean or cladistics methods, but this is food for thought. It may be required to see if chimeras between neognaths and palaeognaths are possible before making a dinobird.
- A Chickenosaurus may not be a true non-avian theropod. Just because they have ancestral features and changed alleles does not change the species. It will still be a bird. To me, a species is dictated by significant change to it's genome. The Chickenosaurus only has changed alleles and gene regulation. Hoatzins and ostriches may have wing claws, but that does not make them a non-avian dinosaur.
- Birds can only develop tooth-like structures that are present in the early development of crocodiles and theropods. They cannot, and will never be able to develop functional teeth with an enamel cap. We could design the genes ourselves, but that would be an artificial trait and not an ancestral trait. I'm not sure if it's possible to reverse-engineer the enamel pseudogenes back into functional enamel. Moreover, the talpid2 virus which allows the birds to grow teeth kills all chicken embryos before they hatch, in a similar manner to how the albino gene kills horses.
Sorry, but I just had to get this off my chest. I have already told people that we can recreate dinosaurs and I don't want to be wrong. It causes me enough stress as it is.
I did not post this in the forum because I felt it would be too long for a single post there.