The Common Ancestry Thread

by cantleave 271 Replies latest members adult

• 

  A Ha

  I think I can understand in a limited way the processes involved as you are trying to explain them. However from my point of view I still don't see how it negates a creator at the beginning, or even during each of those processes. I'm still of the firm belief in intelligent design.

  I guess when it comes to the divide between man and apes (as well as all other animals), to me it's the differences rather than the similarities that cause me to believe in an intelligent designer. Man's spirituality...

  His capabilty of complex languages... His creative abilties... His inbuilt morality... His love of beauty... His abilty to express himself in music... His understanding of history and ..... science

  The evidence presented hasn't negated the possibility of a creator of some sort, but it has overwhelmingly shown that this creator wasn't the Abrahamic god. Man is not a separate creation, apart from the animals. There was no Adam and Eve. There was no "fall" and no need for Jesus' sacrifice. If you want to believe in a sort of Deist god (an impersonal force of some kind that created everything then ignored us afterward), have at it, but this is almost never the case. What we always see is someone making a general Deist argument, then magically attaching all of the Judeo-Christian attributes to this creative force without justifying the leap.

  What you're making is a God of the Gaps argument... an Argument from Ignorance, as Cofty has said (and I want to echo Cofty's sentiment that 'ignorance' is not used as a pejorative; it's the name of a type of argument).

  For centuries, "God" was used to explain everything we didn't have an answer for. God created the sun and moon and made them go around the earth. God made it rain, and brought tornadoes and floods and volcanic eruptions. God taught us language and love and morality and the other intangible, numinous qualities of our existence.

  There were thousands of phenomena used as evidence of a God. But over time we discovered the natural explanations for them. There is no god in the clouds hurling thunderbolts down to earth, etc… Today those thousands have shrunk to just a few questions that science has not yet worked out the answers to. As we figure them out, your list will shrink further.

  In fact, I’d say morality has already pretty much been figured out… at least to the extent that we can come up with pretty good ideas of where it came from. (There isn’t a morality rulebook encoded in our genes. Morality is just a word used to describe how we social animals have learned to cooperate in order to survive and thrive.) The presence of the foundations of morality—reciprocity and empathy—in other mammals shows it’s not something unique to humans… our more complex brains have simply allowed us to come up with more complex moral codes.

  Here’s a fascinating TED Talk about this: http://www.ted.com/talks/frans_de_waal_do_animals_have_morals.html

  There will always be a few gaps that we can insert “goddidit” into, and there is a certain comfort in believing there is someone up there looking out for us individually. But especially after leaving the JWs, I don’t want to believe something because it feels good, or makes me feel special. I want my beliefs to be based on the evidence.
• 

  cantleave

  Please note evolution is not about the existence of a creator, it is the explanation for biodiversity not the origin of life. The origin of life is a completely different field of scientific endeavour known as abiogenesis.
• 

  cofty

  Earlier in this thread there are a number of interesting examples of pseudogenes. These are relics of genes that we inherited from our ancestors but which have fallen into disuse and become disabled through deleterious mutations.

  The rule as far as natural selection is concerned is "use it or lose it". Way back on page 1 Cantleave explained how we lost the ability to produce vitamin C when it became readily available in our diet. With no selection pressure to maintain working vitamin C genes, mutations accumulated unchecked so that we are left with only the broken machinery of vitamin C production in our genome.

  Another interesting example concerns a protein called "myosin heavy chain 16" (MYH16) that is expressed in only a subset of muscles. When this protein is missing or altered the muscle fiber is reduced in size. In the macaque and gorilla MYH16 is made in the temporalis muscle that attaches to the skull and produces the powerful chewing pressure of the jaw.

  In humans MHY16 is also expressed in our temporalis muscle but a mutation in the gene has inactivated the protein's function resulting in muscle fibers that are one eighth the size of our primate cousins. If you put your fingers on the sides of your head now and chew you will feel your modestly-sized temporalis muscles in action.

  Our closest hominid relative, the chimpanzee have an intact MYH16 gene. Since the rate of mutation can be determined, Hansell Stedman and his team at the University of Pennsylvania have calculated that the mutation that disabled the gene in our line happened between 2.1 and 2.7 million years ago.

  So here is an interesting idea. The large temporalis muscle has to attach to very thick and strong skull bones. A loss of MYH16 in our ancestors permitted the brain-case to become thinner and larger allowing for the expansion of the hominin brain which is one of the defining features of Homo sapiens. The genus Homo first appeared around 2 million years ago. Add to that the thought that a reduction in the jaw muscles would likely lead to finer control of the mandible that is required for speech.

  Of course we must be careful not to make simplistic assumptions. A sudden loss of MYH16 in an ancestor would more likely have led to the starvation of that individual than to the sudden appearance of big-brained descendants. The story of the loss of our big temporalis muscle is undoubtedly more complex and interconnected with other changes. However the relic of this gene in our genome is another piece of evidence of our common ancestry with all living things.

  
• 

  Comatose

  Great info! Wish I had gone to college. I would have love to have studied lots of this stuff.
• 

  cantleave

  Some of the strongest evidence for common descent can be elucidated from embryonic development because w atching an embryo develop reveals a great deal about its ancestral history. The study of the developmental history of an organism within its own lifetime is called ontogeny, and when ontogeny is applied to an organism’s ancestral evolutionary history (or phylogeny ), it is known as evolutionary developmental biology or Evo-Devo.

  By comparing analogous features at different stages of development between different species biologists are able to bridge some of the gaps in the story of a creature’s evolution. As is often stated by creationists nobody was present to witnesses the process of evolution and the fossil record although substantive, does not represent a complete catalogue of evolutionary change. Evo-Devo allows us to glimpse in real time some of the developmental processes that lead to the production of distinct features, such as the evolution of feathers in birds. It is another e xquisite corroboration in the vast body of evidence for evolution.

  So what do I mean by comparing analogous features? Well take a look at the picture below. These 4 diagrams of vertebrate embryos show that they all share some common structures, one of which has been labelled “gill slits”.

  

  These embryonic “gill slits”, “branchial clefts” or more accurately pharyngeal clefts make up part of what is called the “pharyngeal apparatus” located in the front and sides of the anterior region of all vertebrates during the pharyngula stage of development. In fish, and the larva of amphibians, these develop into respiratory organs used to extract oxygen from water whilst in reptiles, birds and mammals they are modified into other structures.NOTE: the terms gill slit, or branchial cleft are misnomers. In most vertebrates other than fish or amphibians, these are corresponding or analogous structure to gills but they are not gills and are never used by the embryo in any type of gaseous exchange.

  The pharyngeal apparatus is made up of pairs of external pharyngeal arches and clefts with a corresponding set of interior pharyngeal pouches. These pouches are separated from the external arches and clefts by a membrane (mesoderm). During development the mesoderm differentiates into skeletal (including the bones of the middle ear), muscle and arterial tissues, and each arch becomes associated with a particular cranial nerve.

  Most vertebrates will develop six of these arches during early embryonic development but within weeks these are modified and fused into non-gill related structures. For example in humans, the first of the arch is called the mandibular arch as its name suggests it contributes to the mandibles, the upper jaw and lower jaw , the 5 th arch is transitory and the 4 th and 6 th arches fuse.

  In evolutionary terms the formation of the pharyngeal apparatus reflects the evolution of non-gilled vertebrates from their distant gill possessing aquatic ancestors. The process of evolutionary change has been preserved in the embryological development for all to observe.

  Unfortunately the misnomers such as “gill slit” and “branchial slit” provide the creationists with ammunition to minimize these blatantly obvious structural similarities

  Another example of Evo-Devo providing some interesting proof of common ancestry can be observed in cetaceans (whales, dolphins, and porpoises) embryos. Cetaceans are unusual in that they do not possess hind limbs. However, cetacean embryos do initiate hind-limb bud development, the development of which is arrested followed by subsequent degeneration (in dolphins this occurs around the fifth gestational week). This supports the theory that cetaceans were once land mammals that have returned to the ocean, the presence of the initiation of hind limb development that dolphins had terrestrial ancestors with four limbs, which is further supported by the fossil record, as this video shows.

  http://www.youtube.com/watch?v=o92x6AvxCFg
• 

  besty

  bttt
• 

  LisaRose

  Very interesting reading. I don't know how anyone could look at embryonic development and deny common ancestry.
• 

  zeb

  ... and how was your day...?

  all this amazing scientific wanderings (way over my head) is what? It sounds like the wts itself on its never ending need to be ever proving something.

  No offense have a nice day

  big hugs.
• 

  zeb

  I saw a doco last year that reported on earliest 'man' bones at a burial site in Spain. These were of the era of the neanderthal. But these neanderthal remains of someone buried with ceremony. This believed by the way they were 'layed' and with little trinkets etc proved that neanderthal was not a brute ape like being as we were taught at school but the big question mark was that the bones had different DNA to modern human bones.

  and apart from that its pay day next week at petrol here is 1.64 a litre. (thats x 4.54 to Gallons for the US readers)

  love you all for all your wonderful diversity.
• 

  cofty

  If you make the effort to read this thread you will find its not over anybodies head. Everything is explained using short words and pretty pictures.

  "it sounds very wts" - zeb

  wts - "agree with our dogmatic statements or lose your family"

  Science -"here is the evidence. If you can show it is wrong you can have a Nobel prize"