Pani and his colleagues report that they have found three similar signaling centers in embryonic acorn worms. What are these genetic cues doing in a brainless worm? They appear to be directing the animal's ectoderm, which contains sensory cells, around the circumference of the animal (unlike the centralized nerve bundle found in vertebrates). According to Pani and his colleagues, these cues are not present in amphioxus and its fellow invertebrate chordates, suggesting that they lost them over time.
That would mean that the vertebrate brain "didn't invent entirely new mechanisms—it took existing ones to develop a completely new structure," Pani explains. If the genome is the proverbial set of blueprints for an organism, the signaling centers involved in embryonic development are like the early pieces of the scaffolds. "Vertebrates have that same sort of framework and are turning it into a very fancy Frank Lloyd Wright house, and hemichordates have turned it into a little cottage."
Mixed signals
But not everyone is convinced that these reminiscent signaling centers really are the original beacons signaling early nervous system complexity. The researchers have found gene interactions that are involved in body patterning dividing their heads from their tails—and not much more, says Linda Holland, a research biologist at Scripps Institution of Oceanography who was not involved in the new research. "It's not uncommon for an animal to have part of a gene network" without possessing the entire workup, she notes.
She works with amphioxus and is not convinced that all of these signaling centers are absent from her subjects after all. The suggestion that amphioxus and other invertebrates have lost these signaling centers is "way out of bounds," she says. "I think the amphioxus community is going to be up in arms."
She also is skeptical that the signals Pani and his colleagues found are quite as clear and simple as the paper describes. The genes might be helping to distinguish the worm's front from its back, but possibly no more than that, she notes. "Hemichordates probably have some of [this] machinery in place, but it's much messier" than the findings suggest, she says.
Holland notes that a lot more research—on acorn worms, amphioxus and other extant invertebrates—is needed. And Pani does not write off amphioxus as a first-choice organism for evolutionary research. But researchers shouldn't limit themselves to one model subject, he argues. "If you see things that were different between it and vertebrates, you can't conclude they're unique to vertebrates without looking further."
Looking for ancient ancestors can also help to elucidate how early animals developed their basic body plan and nervous system. "It's still very controversial as to what the nervous system of that common ancestor would have looked like," Pani says. Fossils of 500-million-year-old small, soft-bodied invertebrates can be difficult to interpret. "Not having a time machine, we're stuck," Holland says.
The origin of our complex brains remains controversial, and, Pani says, "I imagine it will stay that way."
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Add CommentHave nematodes not evolved in the past 500 million years? If they have, perhaps 500 million years ago they did not possess the same signalling mechanisms that they have today. On the other hand, some complex organisms, such as alligators and sharks, do not seem to have appreciably changed over perhaps hundreds of millions of years. Not to stir up any creationists, but how do some species avoid significant evolutionary developments resulting from random mutations while others develop dramatic changes? Unlike perhaps nematodes, it seems apparent that the common ancestors of modern ape species did not survive...
Reply | Report Abuse | Link to thisRandom mutation is only part of the process. Many species seem to be exquisitely well adapted to their niche, and being so well adapted, there is likely less advantage to smaller incremental changes. The mud in the sea floor is a fairly consistent, and even though they are by no means stagnant, the worms are as well. A truly dramatic change or mutation, would seem to be far less likely to be beneficial in such a specific environment. Under those circumstances, Natural selection and pressures seem to have less to work on.
Reply | Report Abuse | Link to thisThe human brain is still evolving/reorganizing along molecular-biology lines that depend on diet (eg, acetylcholine, calcium, etc) and stimuli. It began with basic microbial instinct, still operative today in bacteria sending out enzymes to snip off bactericidal drug-molecule tails and/or to thicken their cell walls defensively. We need less studies on nematodes and more insight into human cognition, neuroglia and smart molecules.
Reply | Report Abuse | Link to thisComplexity is a fuzzy word without a proper definition. An atom is complex, a molecule is complex, a macromolecule is complex, a cell is complex, a cluster of cells are complex etc etc. There is no complexity. There is only interference of particles/strings/waves reflected as a measurement of carbon-X entangled states observed via whatever tools are developed. Unless the origin of carbon interference is defined, predicted and measured, the above string of words hold no true scientific 'VALUE'.
Reply | Report Abuse | Link to thisThis makes sense. Since nerve tissue comes from ectoderm, sensory tissue could have moved from the outside of the animal to the inside. Once there, it could have become nerve tissue.
Reply | Report Abuse | Link to thisGenerally, I share your opinion with one exception:
Reply | Report Abuse | Link to thisNatural selection probably had a hard job preventing the species from genetic decaying.
I'm not sure if I understand 'genetic decay,' but as my understanding is only of the most basic kind, I'll answer anyway.
Reply | Report Abuse | Link to thisGenetic decay, or chemical damage, transcriptional errors, and even radiation damage, are always present.
If the mutation is positive, and it can be acted on by selection, then it will be reproduced. If it is detrimental it will likely be eliminated. If it is benign or nonsensical, it may be removed through genetic drift. The negatives tend to act pretty quickly on any reproducing organisms, where the positives have a chance to effect the species.
What we need to remember here, are the large numbers of species in the fossil record, that seem to have survived for millions of years, recognizable, and relatively intact. The simple principal of genetic reproduction, along with the elimination of most undesirable 'decay' in the genome, leaves us with the observations that life is fairly robust; and, that each new copy gets a chance to prove its viability. Yes, catastrophic mutations can occur, as well as insurmountable environmental
events, but the basic pattern of life seems to manage long expanses of time well enough.
Coffey3C@Gmail.com
Too many assumptions. This creationist isn't "stirred up," but I defy anyone to "connect the dots" in this argument.
Reply | Report Abuse | Link to thisOkay, I'll play. I won't even point out that a creationist connecting dots, is sort of an oxymoron.
Reply | Report Abuse | Link to thisWhat do you define as dots, and how would you like
them connected?
In general the invertebrate animals explored many modes of sensory and motor response. This ranged from many segmented limbs, single and double wing sets, social insects and lone predators, to multiple simple eyes, compound eyes and other varieties on sensing and responding to the environment. All this exploratory variety converged on a quadruped limb structure tethered to an autonomic nervous system that reflects emotional behaviour patterns into cerebral awareness. In other words the vertebrates have a greatly enhanced capacity to independently reflect and tailor emotional behaviour patterns according to the needs of circumstance. The reptilian and lower mammalian brains are represented in the Limbic lobe of the human brain such that we sense our vertebrate ancestors emotional intentions and even modify similar patterns of behaviour using the newer cortical hemispheres to which we owe our intellectual capacity. This is not consistent with random mutation and natural selection. There are no six legged lizards or four winged birds. A whole new skeletal, visceral and sensory-motor integration was born anew with the vertebrates with further discrete steps toward conscious creative abilities. The vertebrates had no need to re-explore the invertebrate terrain.
Reply | Report Abuse | Link to thisThese are clearly discrete hierarchical steps up evolutions ladder. Hierarchical order is not consistent with random order and it is evident to some degree in how genes are expressed. For example the Hox genes hierarchically order developmental patterns in both invertebrates and vertebrates but with considerable elaboration in the latter. Heritable epigenetic factors also regulate gene expression along with a host of non-coding RNAs. Most of this is inconsistent with neo-Darwinian theory. Although there is a place for random order it is not the whole picture. See the article http://www.cosmic-mindreach.com/Gene_Expression.html and others on the website for more on this.
But why stop at one species of worm to look for traces of nervous origins? Plants respond to sensory stimuli too, some rapidly such as the Venus Flytrap. But roots also seek out moisture and flowers turn toward the sun. Even bacteria have some degree of sensing and responding to their environment. The point is that forever flogging this hopelessly simplistic Darwinian theory is as mindless as thumping a Bible.
An oxymoron is a person who engages in mindless vilification of an opponent rather than address the scientific issues. Someone who has to be told what the dots represent, and how they should be connected.
Reply | Report Abuse | Link to thisSo, here's how it all works. The dots can be defined as all fossil data relating to unobserved past historical events. How they are connected depends on whether evolution happened a particular way, and not another way, or even whether evolution happened at all.
The great advantage of hypothetical theories relating to unobserved and unrepeatable past events is that these dots can be elastically joined in many and varied ways, as there is no possible way of ever "empirically" verifying what actually happened. What "supposedly" happened in the past therefore depends on the particular presuppositions, inferences, assumptions, conjectures and speculations made.
Scientists interpret the data, and join the dots, differently. The supporters of the "evolutionary continuum" model advocate that the fossil record shows the gradual evolution of life from goo to you. The supporters of "punctuated equilibrium" advocate the sudden appearance of complex life-forms, and the "stasis" of creatures throughout the fossil record.
However, the principle factor to be remembered is that the underlying evolutionary assumption must always prevail. Meaning, the evolutionary hypothesis must always be assumed to be a "fact" from the outset, until "proved wrong". This ensures that all the dots are elastically interpreted, with the dots joined in such a way as to always "prove" evolution is true. Thus, evolutionary presuppositions, explanations, inferences, assumptions, predictions, conjecture, and speculations will always support this overriding naturalistic premise, allowing no other - particularly alternative creationists interpretations.
While the Nobel Committee may not regard science based on "explanations" and unverifiable "inferences" as the real thing, or of the same caliber as testable, repeatable, verifiable and publicly observable empirical science, the scientific community largely thinks otherwise.
Are you serious ???
Reply | Report Abuse | Link to thisRelearn Darwin and Pavlov...
(“Reversible marks on the genome allow honeybees to swap between lives as nurses and foragers.”?
Flip From Head- To Feet- Standing…)
(New Science of Consciousness ? Look underneath the AcademEnglish verbiage…)
Genetics Is Progeny Of Culture
It evolves from survival challenges, from natural selection challenges !!!
I.
Adnauseam Genetics Is Progeny Of Culture
Darwin and Pavlov: it is culture, the ubiquitous trait of all mass formats’ reaction to circumstances, that modifies genetic expressions…
A.
Update Comprehension Of Culture-Genetics
http://universe-life.com/2012/07/20/update-comprehension-of-culture-genetics/
The neural system, including the brain, was evolved by unicells communities (cultures) to react to, exploit, the environments for survival-natural selection.
B.
Tree's leaves genetically different from its roots
http://www.nature.com/news/tree-s-leaves-genetically-different-from-its-roots-1.11156#/comments
C.
The cultures of the roots and leaves, their survival reactions to and exploitation of circumstantial environments, are different, hence their different genetics.
Common sense is the best scientific approach. Plain and simple.
II.
Genome Evolves By Culture, Natural Selection, Not Randomly
A.
Rate of de novo mutations and the importance of father’s age to disease risk
http://www.nature.com/nature/journal/v488/n7412/full/nature11396.html
B.
RNA nucleotide genes are ORGANISMS, life’s primal ORGANISMS.
Genomes are template ORGANISMS evolved by the RNAs for carrying out their - RNAs’ - natural-selection tasks.
All life’s activities originate and evolve for the survival of the RNAs.
THIS is Darwinian evolution.
C.
Modified RNAs expressions are NOT random mutations. Some of them are caused accidents, but not random. Apply Darwinism to them.
There is no randomness in the universe that evolves from all inert mass, singularity, to all moving mass, energy, and probably back again.
Now, after a century of strangled Enlightenment, it’s time to restructure science plans, policies and budgets.
The viable future of humanity is not with natural selection, but with scientism, the follow up of Enlightenment.
Dov Henis (comments from 22nd century)
http://universe-life.com/
Tags: genetic mutations, RNA genes life’s primal organisms, genomes template organisms, natural selection