According to some reports, we share half our genes with a banana (New Scientist, 1 July 2000, pp4-5)! !
How valid and helpful are such comparisons?
Ape to human?
Chance or design?
Comparing human DNA with other DNA
Evolution of DNA
Haemaglobin
How does DNA code for proteins
Human genome sequencing project
Shared functions - similar genes
What is DNA?
What is DNA relatedness?
What is DNA - TO BE ADDED
How does DNA code for proteins - TO BE ADDED
What is DNA relatedness - DNA relatedness compares the DNA of different species, e.g. one could compare the DNA relatedness of say apes, monkeys and man. If DNA of similar species is similar, Evolutionists claim that this is added proof of Evolution. The DNA of one species (say of an ape or monkey) has changed over time (by mutation and or allelic exchange) to another species (say a human). (back to top).
Human genome sequencing project - The recent human genome project (see links for Sanger human genome sequencing) has led to about 85 to 90% sequencing of the human genome but only two chromosomes have been fully sequenced (Nature, Genome special, June 2000, pp983-985; New Scientist, 1 July 2000, pp4-5). The quote below from the web site of Nature magazine shows what a colossal work it was to sequence as much as has been sequenced.
"Twenty years from conception to completion in draft form; the work of thousands of scientists from around the globe; over 90% coverage of our 3.2 gigabase genome. Everything about the Human Genome Project is large scale, including the 62 page report of the International Human Genome Sequencing Consortium which lies at the heart of Nature's genome coverage".
Having completed the project so far, much has been made not of the complexity of our DNA, but the similarity of our DNA to that of less complex animals. and the fact that we apparently only have twice as many genes as worms or flies. Below is a quote from the Sanger web site (see links page).
"The papers published today give us for the first time a near complete set of human genes, which will form the basis for innumerable future investigations. It is estimated that there are only 30,000 to 40,000 genes, confirming the predictions made from the sequencing of chromosome 22, which was completed by the Sanger Center in December 1999. This number, lower than once thought, is only twice as many genes as found in much simpler animals such as worms and flies. Many of the new genes in humans seem to be involved in organising how other genes work". (back to top).
Comparing human DNA with other DNA - Much has also been made of the fact that we have many genes similar to those found in other living organisms. For example, studies have concluded that 75% of human genes or close variants exist in worms, that "we share half our genes with the banana" and that 98.4% of human DNA is similar to that of ape DNA. (New Scientist, 1 July 2000, pp4-5)!
However, it should be known that when comparisons are made between the human genome and other genomes, only short pieces of DNA are compared. Also, to date the entire ape or chimpanzee genome has not been sequenced (Creation News 2000, Vol. 14, No. 2). Sequencing whole genomes of living organisms is horrendously expensive (as one can imagine in view of the time to sequence most of the human genome). To date only the genomes of some bacteria and viruses, yeast, a weed named Arabidopsis and a worm named C. elegans have been totally sequenced and Scientists are close to finishing the sequencing of the Fruit fly and mouse in the year 2000 (Creation News 2000, Vol. 14, No. 2).
So are we a little bit worm, a little bit banana, mostly ape and a little bit human? It is perhaps well to remember the size of the human genome of 3,200,000,000 base pairs as shown in the above quote from the Nature web site. Although we may comprise of only 30,000 to 100,000 (high estimate) genes, each gene can comprise hundreds to thousands of base pairs, and it is the unique sequence of base pairs that makes up a gene. It can take only a few changes in the coding sequence of one gene to completely alter or inactive the function of that gene (see links page for site with details of such mutations). For example, if we have a gene comprising 1,000 base pairs, the function of that gene could be inactivated by a change of only three base pairs (coding for a stop codon to prematurely stop translation of the gene into its gene product). In this example, a less than 1% difference can make the difference between a fully functional gene and a totally non-functional one. (back to top).
Shared functions - similar genes - Our bodies comprise millions of individual cells and each of these cells carry out complex biochemical reactions to perform the tasks relevant for that cell. At an external level we look very different from say a mouse or a banana. However, humans share the same environment as both the mouse and the banana and like the mouse and the banana we require oxygen, some common nutrients, minerals and water for our survival, repair and growth. Thus, there will be some commonality in the biochemical processes that go on within the cell of a human or a mouse or a banana.
Similar biochemical functions will require similar enzymes which in turn will require similar sets of genes to code for such enzymes. Thus, whilst we may look very different from say mice or bananas, we require many similar genes for functions at a cellular level.
In view of the complexity of biochemical systems, many scientists would doubt that such systems could arise by chance. Another interpretation of DNA relatedness might be just that we share a common environment and so at a cellular level there are lots of similar enzymes required. One would not suggest that similarity in car components in different makes of cars was evidence that cars self assemble themselves and evolved from the first car made without the benefit of intelligent design. (back to top).
Haemaglobin - DNA codes for proteins so similarity in proteins (or otherwise) can also be related to similarity (or otherwise) in DNA sequence. Haemaglobin, the molecule that carries oxygen around the body in red blood cells is found in all veterbrates, but also exists in earthworms, starfish, molluscs, in some insects and plants and even in certain bacteria (Blanchard, 2002). However, when scientists examined the haemaglobin of crocodiles, vipers and chicken, they found that crocodiles were more closely related to chickens on the basis of similarity in haemaglobin than to their fellow reptiles (Blanchard, 2002). Other similar examples exist. On the basis of this, the whole idea of DNA (or protein) relatedness being because of evolution falls down. (back to top).
Ape to human? - If the above quoted differences are reliable, then about a 1% difference can result in all the large differences between man and apes or monkeys, including much reduced brain size in apes or monkeys compared to man. If you are 50% out you could end up a Banana! (back to top).
Evolution of DNA - Taking the full range of supposed Evolution from a bacteria with a genome size of about 1,000,000 base pairs to about 1000x as many as that for a human, it would be truly amazing if all the complex sequence changes occurred by random mutational events followed by selection to produce the rich tapestry of life that we see. If these sequence changes did occur by random events, why should there be such similarity between different living organisms. Radiation mutates DNA, but if you irradiate bacteria (or humans or fruit flies) you get damaged, not enhanced versions of the original.
Additionally, there is no proved mechanism whereby bacteria, which don't have a proper nucleolus, mitochondria, golgi bodies, endoplasmic reticulum etc. become single celled eucaryotic organisms (e.g. a protozoa such as amoabae) which have a proper nucleolus, mitochondria etc., let alone a more complex multi-celled organism. (back to top).
Chance or design? - Similarity in DNA sequences, rather than pointing to random mutational events, could be interpreted as pointing to a common designer. (back to top).
Suggested reading:-
Darwin's Black box. The Biochemical challenge to Evolution, by M. J. Behe.
Darwin's Leap of Faith, by John Ankerberg and John Weldon.
The Collapse of Evolution, by Huse
Suggested videos:-
The origin of the races
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