Do humans share over one third of our DNA with daffodils?

[GreyGhost]

I was recently reading through Ann Coulter's lastest book Godless where she attacks evolution. In it she claims that humans share 35% of our DNA with daffodils. She doesn't give a source for this and I tried to find it online. Other than some creationist sites, I found this article.

http://personal.uncc.edu/jmarks/interests/aaa/marksaaa99.htm

Once again, the DNA comparison requires context to be meaningful. Granted that a human and ape are over 98% genetically identical, a human and any earthly DNA-based life form must be at least 25% identical. A human and a daffodil share common ancestry and their DNA is thus obliged to match more than 25% of the time. For the sake of argument let’s say 33%.

The point is that to say we are one-third daffodils because our DNA matches that of a daffodil 33% of the time, is not profound, it’s ridiculous. There is hardly any biological comparison you can make which will find us to be one-third daffodil, except perhaps the DNA.

I don't think the author is a creationist, but it is confusing me. Any help would be appreciated.

[VoxRat]

These "percent the same" numbers in the hands of creationists are exasperating.

Look.

I'm pretty sure I share common ancestry with my brother. Yet all - 100% - of our chromosomes are different from one another; not one is identical. So... does that mean we're not related?

Now move the focus to the opposite extreme. Pretty much every one - 100% - of the nucleotides in my DNA is either an adenosine, cytosine, guanosine, or thymidine phosphate. Just like pretty much every one of the nucleotides in a daffodil's DNA is either an adenosine, cytosine, guanosine, or thymidine phosphate. So... does that mean my genome is identical to a daffodil's?

If these similarities are stated more carefully, e.g.

"if you align the coding portions of a human's DNA with the corresponding coding portions of a chimpanzee's, there is a 99% (or whatever it is) match"

then they can have some meaning. Otherwise not.

[N.Wells]

In cytochrome C, humans and sunflowers differ in about 40 of 106 amino acids, so the statistic cited doesn't sound unreasonable.

If you think in terms of arms, legs, eyes, brains, leaves, flowers, etc., a 25 or 33% similarity may sound surprisingly high. However, if you think in terms of biochemical operation of cells, humans and daffodils are really surprisingly similar. We are made of cells that work the in many of the same ways, with the same biochemical processes. We start as a single cell that grows into a multicellular adult by using genes that turn other genes on and off. We all use cytochrome C to move electrons around. We all develop vesicles and endoplasmic reticulum, and have ways of getting DNA & RNA out of the nucleus at specific times. Our cells move water, CO2, Na+, Cl-, K+, and so forth and so on. Thus a lot of genetic similarity is to be expected.

[Peez]

GreyGhost:
I was recently reading through Ann Coulter's lastest book Godless where she attacks evolution.I don't know how to put this, so I will just go ahead and say it: Ann Coulter is an idiot, unencumbered by integrity. If she tells you that the sky is blue, you should go and look just to be sure. I particularly enjoyed seeing her trying to convince a Canadian journalist that Canadian troops fought in Viet Nam. :rolleyes:In it she claims that humans share 35% of our DNA with daffodils. She doesn't give a source for this and I tried to find it online. Other than some creationist sites, I found this article.

http://personal.uncc.edu/jmarks/inte...marksaaa99.htmOnce again, the DNA comparison requires context to be meaningful. Granted that a human and ape are over 98% genetically identical, a human and any earthly DNA-based life form must be at least 25% identical. A human and a daffodil share common ancestry and their DNA is thus obliged to match more than 25% of the time. For the sake of argument let's say 33%.

The point is that to say we are one-third daffodils because our DNA matches that of a daffodil 33% of the time, is not profound, it's ridiculous. There is hardly any biological comparison you can make which will find us to be one-third daffodil, except perhaps the DNA.I don't think the author is a creationist, but it is confusing me. Any help would be appreciated.Just what is meant by such estimates of similarity is generally not explained in detail. This is because measures of similarity are quite a bit more complex than you might imagine. What is clear from the article that you link to is that the author does not seem to understand genetic comparisons, how they are accomplished or what they mean. He even states "If humans and chimpanzees are over 98% identical base-for-base, how do you make sense of the fact that chimpanzees have 10% more DNA than humans?" but still does not figure out that his simplistic notion of comparing bases is just not what biologists do. There are a number of other odd statements in that article:Gorillas and humans do not form a single population any more than gorillas and kangaroos do.Playing with words, or clueless (I cannot decide which). If we killed off all dogs except for Great Danes and Chihuahuas, we could claim that they do not form a single population. Yes, but so what? Nobody has claimed that gorillas and humans form a single population, but it is clear that there has been a continuum between us.Given a human and chimpanzee, you can easily tell them apart, but given only their DNA, you can't tell them apart.Just plain false.If you want to know how similar a human and chimp DNA sequence is, you simply add up the matches.Only if you are ignorant, there are far better ways to compare sequences.They're not 98% physically identical, they are 100% identical, if your frame of reference is an echinoderm.Not just false, this is stupid.

Anyhow, I am not a fan of Wikipedia, but Sequence alignment (http://en.wikipedia.org/wiki/Sequence_alignment) has an overview of a few of the ways in which one can compare DNA sequences (enough to give an idea of how complex the process can be). However, no matter how one compares the DNA, it is not the similarity per se that is of interest here. Rather, it is the pattern of similarities. Chimpanzees are genetically more similar to humans than chimpanzees are to gorillas. Does this mean that chimps should look more like us than gorillas? Of course not! Whales are more genetically similar to sheep than they are to fish. What these patterns of similarity point to is common ancestry. Chimpanzees share a more recent common ancestor with us than with gorillas, so there has been less time for changes in DNA sequences to accumulate. Similarly gorillas are more similar to us than they are to whales, etc. Evolution does not predict any specific level of similarity between chimps and humans, or between daffodils and humans, it is the pattern of similarities that exactly matches what evolution predicts.

Peez

[Straight Hate]

It sounds like she's willfully misinterpreting the idea, but on the other hand, I think it may raise a decent point for those of us not well-versed in biology, but who want to learn more.

I think it was referenced above - if not explained entirely - the disconnect between the idea that my DNA is different from my siblings', yet generalizations occur in grouping entire species together for comparison to other species (i.e. the human/chimp 98% sharing).

The question, then - to reiterate for clarity's sake - is by what mechanism/context/scale do scientists use as a standard for making such general comparisons?

[VoxRat]

The question, then - to reiterate for clarity's sake - is by what mechanism/context/scale do scientists use as a standard for making such general comparisons?Clarity thanks you.

Unless it's stated clearly what is being compared (all DNA? expressed genes? only the exons of expressed genes? particular genes, like cytochrome C?...) and how it's being compared (e.g., how are gaps accounted for?) the number is meaningless.

[Oolon Colluphid]

Well, Steve Jones has often wryly responded to the point that we share 98.4% (or whatever) of our genes with chimpanzees by noting that we also share 50% with bananas. His point is that it's not so much what you've got as what you do with it... though as humans are equally closely related to daffs and bananas, I'll take Jones's 50% over Cootie's 35% any day ;).

The central point is that, at a biochemical and cellular level, there's not a great deal of difference between species... any species really. I forget the exact quote (keep meaning to double-check it), but Colin Tudge makes this point forcefully in his marvellous The Variety of Life (http://www.amazon.com/exec/obidos/ASIN/0198604262/thesecularweb/): from the POV of a biochemist or geneticist, it barely matters whether one studies a bacterium or a butterfly, Plasmodium or a person.

I'm aware that it's a bit more complicated than that (for which see eg Carroll's Endless Forms Most Beautiful (http://www.amazon.com/exec/obidos/ASIN/0393060160/thesecularweb/)), but there is the simplified answer. Most of what it takes to build and run an organism is pretty similar across all life. Hence, a considerable genetic similarity between, eg, Ann Coulter and a cockroach.

Though there could be another reason for that.

[Godless Dave]

I was recently reading through Ann Coulter's lastest book

Why the fuck would you do that?

[Gressil]

I was recently reading through Ann Coulter's lastest book

Why the fuck would you do that?

Because it beats sticking red hot pokers in your eyes (just).

[Jet Black]

I was recently reading through Ann Coulter's lastest book

Why the fuck would you do that?

a fine question, but not entirely relevant to the conversation though :D

[Jet Black]

Why the fuck would you do that?

Because it beats sticking red hot pokers in your eyes (just).


I think we'd need to open a poll to decide on that (no, don't please, at least not in E/C)

[Martin B]

Creationists (among others) are notorious for confusing percent DNA similarity with other measures. For instance, something like 90% of our genes (I don't have the reference or the exact fig, but this works for the sake of argument) are shared with sponges. Or at least that's a line that might be used to summarize the fact that we humans, as compared to sponges, have very little in the way of genes that are actually unique. Most can be homologized readily with genes from a sponge. This is far different from, say, our sharing 90% of our DNA with sponges. I've seen creationists (especially the Jail Bird) confuse this many times.

[Jet Black]

to make a similar comparison, you could make an argument that we only really have about 1000 genes*, since all the others are just variants and homologues of these genes. There's only so much that genes can do to regulate metabolism, growth rates and so on, so there aren't going to be an incredible variety of them

*there are about 1000 families of closely related genes.

[Jet Black]

Whenever this sort of thing comes up in discussion, always ask what metric they are using. If they can't tell you, then point out that they can't make a comparison unless it is really clear on what basis they are making a comparison. See you could argue that on a metric of basic chemicals, all DNA is absolutely identical, because it all uses the same bases, on a metric of gene familes, they might be related 33% but on a metric of chromosomal stucture they might only be 1% similar for example. The making of comparisons without a clearly defined basis is utterly worthless.

[lpetrich]

I doubt that there's been much research into daffodil genetics. The common daffodil is classified as Narcissus pseudonarcissus, and I searched PubMed (http://www.pubmed.org) for articles on it.

daffodil - 95 hits
narcissus - 210 hits, including some on the psychiatric disorder of narcissism
pseudonarcissus - 48 hits

So there has not been much work on daffodil genetics.

By comparison, the lab rat of plants, the mustard weed Arabidopsis thaliana, has 19009 hits, with Arabidopsis alone having 21743 hits.

On the subject of proteins shared across eukaryotedom, I've found A comprehensive evolutionary classification of proteins encoded in complete eukaryotic genomes (http://genomebiology.com/2004/5/2/R7), by Koonin EV, Fedorova ND, Jackson JD, Jacobs AR, Krylov DM, Makarova KS, Mazumder R, Mekhedov SL, Nikolskaya AN, Rao BS, Rogozin IB, Smirnov S, Sorokin AV, Sverdlov AV, Vasudevan S, Wolf YI, Yin JJ, Natale DA.

From Genome Biology, v.5(2); 2004

They looked at the genomes of these species:

Caenorhabditis elegans - lab nematode
Drosophila melanogaster - lab fruit fly
Homo sapiens
Arabidopsis thaliana
Saccharomyces cerevisiae - brewer's yeast
Schizosaccharomyces pombe - fission yeast
Encephalitozoon cuniculi - microsporidian

and used the 5873 clusters of predicted eukaryotic orthologous proteins (KOG's) from previous work. They found that about 40% of them are shared by 6 or 7 species, and that many of them are involved in such housekeeping functions as translation and RNA processing.

So we do share a lot of genes with Arabidopsis plants, but what about daffodils?

Narcissus pseudonarcissus is closest to Arabidopsis, of course. Both are angiosperms (flowering plants), but Arabidopsis is a eudicot, and the daffodil is a monocot. This suggests that Arabidopsis is a good proxy for daffodils here.

So Ann Coulter's claim is not too far off in certain ways, and is not the self-evident absurdity that she hopes that her readers will conclude.

Gene-sequence similarity is much less, of course, with only the more conserved domains remaining recognizably similar between us and daffodils. And organization and patters of duplication are also very different. Which makes the overall numbers even worse.

[Boro Nut]

I was recently reading through Ann Coulter's lastest book Godless where she attacks evolution. In it she claims that humans share 35% of our DNA with daffodils.As other posters have already pointed out, it depends entirely on the specifics under consideration. For instance, are the daffodils behind a bus stop? How quickly does DNA evaporate? Does piss even contain DNA?

Boro Nut

[Oolon Colluphid]

I spotted these daffs by a lake
And a fine pretty picture they make
And so every now and then
I think of them again.




(Roger McGough's take on Wordsworth, paraphrased from memory)

[GreyGhost]

I was recently reading through Ann Coulter's lastest book

Why the fuck would you do that?

Some guy sent it to me in a PDF file and asked if I would look over the evolution chapters quickly. It's bad. Really bad. The daffodil claim was the only one I hadn't heard before, the rest are "no transitional fossils" and Piltdown man. Just let me select you a few gems from the book.

Moreover, if all species evolved from the same single-celled organ-ism beginning in the same little mud puddle, why hasn't the earth-worm made a little more progress? Was it never, ever desirable in any of the worm's many dirt holes to mutate eyes or legs or wings or a brain? How could one clump of cells starting in the same little puddle become a human being while others never make it past the amoeba stage? Forget getting to humans, which liberals rank as the lowest form of life. Why hasn't the earthworm evolved into a beagle? Just for being cute, a beagle can acquire a six-room coop apartment on Park Avenue, surely an evolutionary advantage.

Yes, today there are thirteen species of finches on the Galapagos Islands. Guess how many there 150 were when Darwin first discovered them in 1835? That's right! Thirteen species. Darwin hypothesized that the thirteen species he found might have "evolved" from one species, just as evolutionists hypothesize that the bat might have "evolved" from a clumsy squirrel. The Galapagos finches are evidence of nothing but the evolutionists' ability to make up stories.

If anything, the finches are a major blow to Darwin's theory of evolution. Despite major changes in the environment on the Galapagos Islands, the formation of new species has never been observed there. There were thirteen species in 1835, and after more than 170 years of wild variation in the environment, mutation, and "natural selection," there are still thirteen species. The finches' beaks have moved back and forth in shape and nothing more.

The sad thing is that this drivel was a bestseller. How many people swallowed this nonsense hook, line, and sinker?

[Oolon Colluphid]

Moreover, if all species evolved from the same single-celled organ-ism beginning in the same little mud puddle, why hasn't the earth-worm made a little more progress?
Well that's novel. "If we evolved from single-celled things, why are there still worms?" Heh, even AiG must be embarrassed by her.
How many people swallowed this nonsense crook, lie, and stinker?
Fixed it for you.

[lpetrich]

First, Arabidopsis being a eudicot and the daffodil being a monocot implies that their ancestors parted ways in the Jurassic or early Cretaceous, which is well after when the ancestors of our species, fruit flies, and nematodes had parted ways (late Proterozoic?).

Moreover, if all species evolved from the same single-celled organism beginning in the same little mud puddle, why hasn't the earth-worm made a little more progress? Was it never, ever desirable in any of the worm's many dirt holes to mutate eyes or legs or wings or a brain?
Earthworms do have nervous systems and light-sensitive cells. However, they live underground, so they have little selection pressure to develop improved vision. In fact, underground animals often have poor eyesight and are sometimes blind; their eyes degenerate.

How could one clump of cells starting in the same little puddle become a human being while others never make it past the amoeba stage?
Adaptive radiation. Ms. Coulter ought to look at the numerous breeds of domestic animals and cultivated plants. Their masters select for different things, thus producing all this variety. And something similar happens in the wild.

Charles Darwin had pointed out the Galapagos finches as an example of adaptive radiation; after some finches made it to the Galapagos Islands a few million years ago, different groups of their descendants went in different directions, becoming adapted for eating different sorts of food.

Forget getting to humans, which liberals rank as the lowest form of life. Why hasn't the earthworm evolved into a beagle? Just for being cute, a beagle can acquire a six-room coop apartment on Park Avenue, surely an evolutionary advantage.
It would require a Hades of a lot of evolution to get from an earthworm to a beagle. And what may be an advantage in one environment may be a disadvantage in another environment.

Beagle dogs are a hunting-dog breed, meaning that they have been artificially selected for helping their masters hunt. And like other dogs, they have been artificially selected for being nice pets.

(a lot of haranguing about the Galapagos finches snipped)

[-RRH-]

I also like how the quote is "For the sake of argument let’s say 33%."

And then once the creationist rumour-mill is done with it, it's a cold hard fact, not a number that Jonathan Marks pulled out of thin air.

[Llyricist]

I spotted these daffs by a lake
And a fine pretty picture they make
And so every now and then
I think of them again.




(Roger McGough's take on Wordsworth, paraphrased from memory)

Every time I see or hear the word Daffodil, I flash back to the moose's take on Wordsworth.