Scientists give insight into 200-year-old riddle

Dec 10, 2010
Scientists give insight into 200-year-old riddle

(PhysOrg.com) -- University of Manchester researchers have played a vital role in an international study that has revived the 200-year-old question: why do different species share similar stages of embryonic development?

Dr Casey Bergman and Dr Dave Gerrard at Manchester’s Faculty of Life Sciences collaborated on the project with Pavel Tomancak, at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, and Uwe Ohler, at Duke University, on a study funded by the Human Frontiers of Science Program published in Nature today.

The team looked at differences in the embryonic development of species in search of what unites animal groups at the level of embryos and their genes, bringing the power of modern molecular techniques to bear on what is a classic problem in biology.

It has long been noted that there are striking similarities between the embryonic development of animals and their evolutionary histories. This relationship between how animals develop and deep evolutionary time hints at the existence of profound connections between different animal species and has therefore captured the imagination of both biologists and the wider public.

However, ever since the first observations were discussed by leading 19th century biologists, such as von Baer, Darwin, and Haeckel, the existence and meaning of these similarities has been fraught with controversy arising from the subjective nature of the comparisons of different animal forms.

While the pioneers of embryology believed that animal species are most similar at the earliest stages of their embryonic development, the arrival of improved observational methods in the 20th century led to a revised proposal. It was noticed that the middle periods of embryonic development exhibit the highest similarity between species belonging to the same broad taxonomic group, known as a ‘phylum’, with earlier and later periods often showing remarkable divergence in form. This so-called 'hourglass model,' has so far been supported by the same types of evidence available to 19th century biologists, namely subjective comparisons of embryo appearance.

Taking advantage of advancements in large-scale gene-based methods, the international team compared the embryonic development of six different fruit fly species at the molecular level. Instead of subjective assessment of a handful of visible traits, they made objective measurements of expression levels for several thousand genes.

The team found that the developmental period when insects are most similar in form is indeed underpinned by a corresponding similarity in gene expression. “This discovery both confirms the conclusions of previous anatomical studies and extends our understanding of the relationship between development and evolution to the molecular level,” explained Dr Kalinka, who led the analysis of the data.

The team also shed light on the reason why there is a period of similarity in the middle of animal , a fundamental problem that has so far remained unanswered. Dr Bergman explained: “Our study provides the first solid evidence that this period of similarity between animal species is being actively preserved by natural selection as opposed to being a period that is simply resistant to change for other reasons.”

The results open up new horizons, as the fruit-fly species used are one of the best-studied experimental model systems for genetics, development and evolution. Detecting the hourglass pattern among such closely related species is for biologists equivalent to obtaining a time machine into processes that led to the initial branching on the animal tree 600 million years ago, as these are very much alive today and can be probed and studied by modern technologies such as genome manipulation and high-resolution imaging. Pavel Tomancak, who led the study, concludes: “In the future we hope to use these new tools to gain deeper insight into the evolutionary processes that shaped the remarkable diversity of animal forms observed today.”

Explore further: Testing shows billfish demonstrate bone remodeling without osteocytes

More information: The paper ‘Gene expression divergence recapitulates the developmental hourglass model’ (Nature, December 9, 2010) is available at www.nature.com/nature/journal/… ull/nature09634.html

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dogbert
1 / 5 (12) Dec 10, 2010
“Our study provides the first solid evidence that this period of similarity between animal species is being actively preserved by natural selection as opposed to being a period that is simply resistant to change for other reasons.”

How does natural selection have an agenda? How does it "actively" seek anything?
LivaN
4.8 / 5 (13) Dec 10, 2010
It's a figure of speech.

When you read a book and there is a phrase such as, "the wind moaned violently on such a lonely winter night"
Do you presume the wind to be a person or animal that can moan? Do you think the winter feels lonely? No.
dogbert
1.3 / 5 (13) Dec 10, 2010
No, it is not a "figure of speech". The phrase "actively preserved" indicates directed activity. Natural selection, buy definition, is not seeking or directing anything.
M_N
1 / 5 (5) Dec 10, 2010
Why did Physorg choose to accompany the article with Haeckel's fraudulent (and thoroughly discredited) drawings of embryo development? Actual embryos are nowhere near as similar as this drawing suggests.
kevinrtrs
1.3 / 5 (24) Dec 10, 2010
It's a figure of speech.

No, it's not. Evolutionists like to use these terms to mean one things and imply another.

They know quite well that these similarities were fraudently put across by Haeckel but because it's not been removed from school textbooks and the lie has been shamelessly propagated they are now trying to once again justify it.

I suppose if you repeat a lie often enough it becomes accepted by the general public that don't know any better. Just like the theory of evolution is probably the biggest lie perpetrated on the human race.
Skeptic_Heretic
4.8 / 5 (19) Dec 10, 2010
They know quite well that these similarities were fraudently put across by Haeckel but because it's not been removed from school textbooks and the lie has been shamelessly propagated they are now trying to once again justify it
Maybe in school districts that are underfunded.
Haeckel's drawing were explicitly stated to be in error in my school textbooks and that was over 15 years ago.
Just like the theory of evolution is probably the biggest lie perpetrated on the human race.
Evidence your alternate hypothesis of giants who lived for millenia and an Earth that was younger than the oldest of them, moron. Your textbook can't even get well known math of the time correct. pi != 3.
Raveon
4.8 / 5 (18) Dec 10, 2010
Get your heads out of the bible and read some other books. It makes about as much sense you commenting on science as it does me doing a dissertation on the bible. Which is to say none at all.

You people constantly hitting on evolution says more about your innate insecurities than it does about science, deep down you are a disbeliever in your religion and argue against science as an unconscious reaction to that core disbelief that you can't even acknowledge to yourself.

I went on a cruise once and met the piano player. He had a doctorate in theology, ex minister. I asked him what he was doing on a ship playing piano. He said he had to be intimately familiar with the Koran and other works besides the bible to get a PHD. When he was done he found so much BS and contradiction in the bible and the other books that he lost his religion and became a piano player.
KBK
2 / 5 (1) Dec 10, 2010
No, it is not a "figure of speech". The phrase "actively preserved" indicates directed activity. Natural selection, buy definition, is not seeking or directing anything.


Actually, no one ever said that 'natural selection' was passive. It is assumed but in hypothetical situations, the data can take interesting paths. that's the whole point. It has not been discovered and proven in the realm of science that natural selection is 'active' but there is no reason to not test the hypothesis. However, doing that would be tricky, one might guess..

If it were found to be an active participant, it might take a direction that is similar to that of the ACO or 'ant problem solving methodologies.'

Just a shot in the dark, but it would be difficult to gather such a data set. It might be testable in fruit flies.
Skeptic_Heretic
5 / 5 (11) Dec 10, 2010
It has not been discovered and proven in the realm of science that natural selection is 'active' but there is no reason to not test the hypothesis.
Natural selection is an active and a passive process. Natural selection is what happens whn a population is under pressure. If that pressure is passive, like resource quantity, then Natural selection takes a passive role. If that pressure is active, like predation or sexual selection, natural selection takes an active role.
Quantum_Conundrum
2.3 / 5 (3) Dec 10, 2010
Maybe in school districts that are underfunded.
Haeckel's drawing were explicitly stated to be in error in my school textbooks and that was over 15 years ago


When I was in college 9 to 12 years ago, those drawings were still being presented as allegedly "indisputable facts" in support of evolution.
Skeptic_Heretic
5 / 5 (6) Dec 10, 2010
Maybe in school districts that are underfunded.
Haeckel's drawing were explicitly stated to be in error in my school textbooks and that was over 15 years ago


When I was in college 9 to 12 years ago, those drawings were still being presented as allegedly "indisputable facts" in support of evolution.
Which college? Colleges are private institutions and can teach whatever they choose. If it was a state college, you should have complained.
EdMoore
3.3 / 5 (4) Dec 10, 2010
To Skeptic...

"Your textbook can't even get well known math of the time correct. pi != 3."

When you go through the dimensions of the wash basin in the temple, and account for the handbreadth thickness of the rim, pi is accurate to three or four decimals... I went thru the math on that a few years ago...
Skeptic_Heretic
5 / 5 (11) Dec 10, 2010
To Skeptic...

"Your textbook can't even get well known math of the time correct. pi != 3."

When you go through the dimensions of the wash basin in the temple, and account for the handbreadth thickness of the rim, pi is accurate to three or four decimals... I went thru the math on that a few years ago...

Do you commonly measure diameter to the outside of a vessel and circumference on the inside or do you use a universal reference point?

Cubit= 18 inches
Hands breadth= 4 inches
total circumference to the outer rim = 540 inches
total diameter outer rim = 180 inches
total radius outer rim = 90 inches

C=2(pi)r
540 inches=2(pi)90
540/(2)90=3
pi != 3

Making arbitrary changes to force a fit after post retranslation is what we call, fudging the numbers.
genastropsychicallst
1 / 5 (9) Dec 10, 2010
Why inside ? To outside the heredity of private parts between riddles be !
pauljpease
5 / 5 (10) Dec 10, 2010
No, it is not a "figure of speech". The phrase "actively preserved" indicates directed activity. Natural selection, buy definition, is not seeking or directing anything.


No, you're adding the words "seeking" and "directing". Natural selection is a process, or mechanism. In this case, "actively" means that it is a result of a current or ongoing process. Like a light bulb. It can be off (inactive) or on (active). Saying that a light bulb is actively providing light doesn't mean it is "seeking" or "directing" anything. It just means it is currently "active". The researchers have found that natural selection is currently operating to keep this particular stage of development relatively constant compared to other stages of development. So this stage is being "actively preserved by natural selection". They mention that it could have been preserved by mechanisms other than natural selection, but apparently natural selection is the "active" mechanism in this particular case.
dogbert
1.7 / 5 (10) Dec 10, 2010
paulipease,

Neither science not natural selection is an entity. Neither can "actively preserve" anything.

I often wonder why people who call themselves scientists must insist that natural processes are intelligent or self directing. The whole premise of natural selection is that it is not self driven.

thales
5 / 5 (7) Dec 10, 2010
Dogbert. Can you name something that natural selection does do? Does it, say, naturally select?
PinkElephant
5 / 5 (8) Dec 10, 2010
@dogbert,

A bacterium actively repairs its own DNA. Is a bacterium intelligent or self directing?

Your syntactic quibbling is pointless and bordering on trollish. The gist of what you object to, is that either the mid-stage embryo shape doesn't change much because of inherent genetic constraints (which for instance cause the embryo to self-destruct or trigger a miscarriage), or the mid-stage embryo shape does mutate just as much as all other stages but only the shape-conserving variants survive under selective pressures and/or develop successfully into successfully reproducing organisms. Apparently, evidence points to natural selection as the relatively more significant cause of shape-conservation at this stage of embryonic development. That's the long-winded expansion of the succinct turn of phrase to which you've objected.

Unless you want all pop-sci articles to be written in lawyer-speak, and to therefore be unreadable, you must learn to see past the vernacular.
dogbert
2 / 5 (7) Dec 11, 2010
PinkElephant,

A bacterium is a living creature. Natural selection is a process.

A living creature is expected to direct its activities to varying degrees. A process is just a process.

The article notes as do you that the mid-stage embryo shape is persistent. Where the article introduces foolishness is in attributing the cause of that persistence to natural selection actively preserving that shape.

The observation that "I see this, therefore natural selection must want this to exist" is foolishness. It is not scientific in the least. If you want to attribute something to natural selection, you must at least show why that trait is selected -- it is definitely not because natural selection wants to select it.
dogbert
3 / 5 (4) Dec 11, 2010
thales,

"Dogbert. Can you name something that natural selection does do? Does it, say, naturally select? "

You should really try to understand that natural selection is, by definition, a process. It is not an entity. It does not make decisions or direct activity. It is simply a process. Organisms with high numbers of detrimental attributes tend to die. Organisms with beneficial attributes tent to live and reproduce. There is no "natural selection" entity sorting through the organisms picking out good ones and killing bad ones.
Ethelred
4.3 / 5 (3) Dec 11, 2010
Your syntactic quibbling is pointless and bordering on trollish.
I agree with him. It is sloppy writing however not some plot. I am not sure which way Dogbert is thinking on this.

Natural Selection is NOT directed. So calling it active is wrong. Even if it is from predation the results of the selection are still not directed as the predator is certainly not trying to cause the target species to become harder to catch.

Nor is Selection passive. Active and passive are poor terms for a process that has no actual goal. It is a name for something that happens without will or intent and passive and especially active implies an intent.

The catch is that it is VERY difficult to communicate at all about anything without using terms that imply intent. Sloppy writing is endemic in biology and I am not sure if there is good way to stop it due the difficulty of doing that while trying to keep people's interest.

Why are you guys giving Dogbert ones for telling the truth?

Ethelred
dogbert
3.4 / 5 (5) Dec 11, 2010
Ethelred,

Thanks. The problem with sloppy writing is that it generally follows from sloppy reasoning. People begin to believe what they say and others begin to misunderstand.

Did anyone notice that the article attributed the observed mid-stage embryo shape persistence to natural selection "actively preserving" it, with no explanation as to how or why the shape was preserved? That is, the "scientific article", by using vague and misleading words, covered up the fact that the study actually discovered nothing about the process.

I do understand and agree that language is imperfect and that it is sometimes better to use incorrect terms when everyone understands the use. For example, it is concise to note that an atom wants to have a full set of valence electrons. When saying something like that, it is understood that an atom has no desires, but that chemical bonds which result in atoms with a full set of valence electrons are more stable chemically.
PinkElephant
5 / 5 (2) Dec 12, 2010
@dogbert,
A bacterium is a living creature. Natural selection is a process.
A bacterium is a conglomeration of organic compounds, and the processes that guide their interactions. It is merely a more complex process, hierarchically composed of simpler ones. The same can be said about any life form, until you get to intelligent life. Intelligent life can be said to be "active" in a very specific way: there is a COGNITIVE process involved amid all the others.

However, if we're going to restrict the "active" language to only circumstances that involve sentient life, then we're going to find it very difficult to discuss anything at all. After all, most of our language and idioms derive from human relationships and circumstances, and therefore our thinking is loaded with "active" concepts.

As I said before, you could try to sterilize the language, but by the time you're done, the result will be pretty unreadable and in practice, unused and discarded.
Ethelred
5 / 5 (2) Dec 12, 2010
However, if we're going to restrict the "active" language to only circumstances that involve sentient life, then we're going to find it very difficult to discuss anything at all.
Well let me have a wack at it.

Original
Our study provides the first solid evidence that this period of similarity between animal species is being actively preserved by natural selection as opposed to being a period that is simply resistant to change for other reasons
My improved version

Our study gives us solid evidence, for the first time, that this period of similarity between animal species is being preserved, by the process of natural selection, via the inherently heartless and amoral killing of all embryos that have the temerity to carry mutations that might create hopeful monsters, as opposed to being a period that is simply engaged in a non-sentient siege mentality against change of any kind.

That ought to do it. Killing, amorality and sieges by Chinese Room processes.

Ethelred