24 Million Generations! Evolutionary Change in Body Size on Earth --From Mouse to Elephant

 

          

Evolutionary changes in body size take a very long time. A mouse-to-elephant size change would take at least 24 million generations based on the maximum speed of evolution in the fossil record,  Becoming smaller can happen much faster than becoming bigger: the evolution of pygmy elephants took 10 times fewer generations than the equivalent sheep-to-elephant size change.

New research also shows it took about 10 million generations for a cat-sized terrestrial mammals to evolve into the size of an elephant. Sea mammals, such as whales took about half the number of generations to hit their maximum.

Led by Dr Alistair Evans of Monash University's School of Biological Sciences a team of 20 biologists and palaeontologists discovered that rates of size decrease are much faster than growth rates. It takes only 100,000 generations for very large decreases, leading to dwarfism, to occur.

Dr Evans, an evolutionary biologist and Australian Research Fellow, said the study was unique because most previous work had focused on microevolution, the small changes that occur within a species.
"Instead we concentrated on large-scale changes in body size. We can now show that it took at least 24 million generations to make the proverbial mouse-to-elephant size change – a massive change, but also a very long time," Dr Evans said.

"A less dramatic change, such as rabbit-sized to elephant-sized, takes 10 million generations."The paper looked at 28 different groups of mammals, including elephants, primates and whales, from various continents and ocean basins over the past 70 million years. Size change was tracked in generations rather than years to allow meaningful comparison between species with differing life spans.

Dr Erich Fitzgerald, Senior Curator of Vertebrate Palaeontology at Museum Victoria and a co-author, said changes in whale size occurred at twice the rate of land mammals."This is probably because it's easier to be big in the water – it helps support your weight," Dr Fitzgerald said.Dr Evans said he was surprised to find that decreases in body size occurred more than ten times faster than the increases.

"The huge difference in rates for getting smaller and getting bigger is really astounding – we certainly never expected it could happen so fast!" Dr Evans said.

Many miniature animals, such as the pygmy mammoth, dwarf hippo and 'hobbit' hominids lived on islands, helping to explain the size reduction.

"When you do get smaller, you need less food and can reproduce faster, which are real advantages on small islands," Dr Evans said.

The research furthers understanding of conditions that allow certain mammals to thrive and grow bigger and circumstances that slow the pace of increase and potentially contribute to extinction.

The Daily Galaxy via  Monash University

Image credit: Image: Alistair Evans and David Jones

Comments

[jiff]

this is nature! nothing came from anything.. scientist researches based on some evidence they have got. but, In reality, its nature. No one can change. But, you can destroy it. Scientist says that human from monkey? but, why still there are monkey? Human DNA and monkey DNA doesnt match. But, Pig's DNA and human DNA matches. So, human came from Pig? Doesnt matter how many generation passes, nothing will transform to anything.. it will remain unchange until the world's end....

[ttyp00]

jiff, surely you have submitted an academic paper on your hypothesis that has supporting evidence and is ready for peer-review? I mean, to make an assertion as you have, you must certainly have evidence that no one has ever seen before! Put up or shut up!

[Elephant]

24 million generations would leave many skeletons to prove such huge change, called evolution.
Based on the lack of such evidence, evolution is better to be called hypothesis, not a theory.

[SB]

Jiff is half right (in a way), there are many flaws in the Darwin evolutionary model. Like there is no evidence of transitional species from fish or amphibians to reptiles, or reptiles to mammals ... and so on.

Most changes in the genetic pool that humans have observed falls under the process and within the limits of epigenetics which is a change in the expressed genes brought on by environmental factors. Where the start and stop indicators on the genes change without any significant change to the entire gene structure. Speciation, which differentiates lets say a dog from a cat where no viable offspring can be produced between the two different species, has never been observed, mathematically the rate of change doesn't support the observed rate change in the fossil record, and an entire books worth of contradictory information that should not be swept under the rug by the close minded.

The search is for the correct answer not settling for a subjective best answer. This is true for both ID an evolutionists, both sides need to weigh/discern between observed facts, assumed facts and biased opinions.

[Frank]

Wow Jiff, amazing that someone can be so ill-informed and ignorant at the same time.

First, human vs human DNA. Any one human compared to another has around a 99.9% DNA match.
Humans vs Chimpanzee. Around 99% match.
Humans vs Pig. Around 88% match.
Humans vs Carrot. Around 50% match.

So no, we are not even close to pigs other than basic mammal stuff like we both breath air.

And as far as the "why are there still monkeys" of course shows your complete ignorance of even the most simplest and basic concepts of evolution.

To answer your question. My ancestors came from France, so why are there still French people? See how dumb that sounds.

My suggestion to you is to spend some time at:
www.talkorigins.org

Then your post may not be so laughable.

[SB]

Sorry Frank, your response to Jiff's post isn't much better.

In theory, you could create a viable offspring in France but I'm willing to guess not with a chimp - ridiculous analogy, I suggest you find a better educational source than web blogs where 90% of what's posted is the ignorant leading the ignorant.

Pig hearts and livers will transplant into humans, and in some cases, will do better than chimp or baboon organs. Even though Jiff got it mostly wrong, there is a bit of truth there.

Don't be so quick to judge others knowledge base when yours is no shining star either.

[Frank]

Well first, let's keep something in mind. Nothing in evolution states that humans evolved from monkeys. Instead, we both evolved from a common ancestor.

Next, the France example is a good analogy. Evolution that results in speciation is generally caused by geographical separation. In other words, there was a split in the population of our human/monkey common ancestor and one of these divisions evolved into humans, the other into apes. To say that since one of the geographically separated groups evolved into humans that the other group would no longer exist is patently ridiculous. And since evolution happens, albeit in a small way, through each and every reproduction cycle, we have indeed evolved in small ways differently than the population of the geographically separated group in France. However, because humans are able to move about the world with ease, my guess is that speciation from geographical separation will most likely not happen between humans in the US and those in France. If we were separated for hundreds of thousands or millions of years, you indeed would expect to see huge differences in the two groups. But once again, you would not expect one group to disappear just because the other evolved into a different species.

As far as pig heart transplants, indeed this has been tried and may even work some day, however, every patient that this has been tried on has died within a couple of days because of rejection of the organ. So bad example. Genetically a pig is quite different than a human.

[SB]

What you mentioned is one of the biggest part of what is wrong with the theory of evolution. It is assumed that speciation does occurs: fact - it has never been witnessed in nature. There is no evidence biologically that a single genetic line and split into two distinct new lineages that can no longer reproduce with each other with separate viable offspring.

Dogs have a generation span of about one year, humans about 20. Domesticated dog have been separated from wolves for at lest 40,000 years or 40 K generations and can easily reproduce with wolves and no genetic consequences. Extrapolating, that would allow humans from today to have the same genetic makeup as humans nearly 1 million years ago. If million year old DNA could be found, it might shed a light on the answer but the best observations to date is the K9 lineage and it's evidence does not translate to the rate of mutations need to support the fossil record change. The K9 argument is not an anomaly, it seems to be the norm.
Then there is the biogenesis question. Life started - fact. Two options, either spontaneous from non-life of by ID, for the theory of Darwin evolution to be true life from non-life is the only option. Knowing even the simplest interactions of cellular biology, one would understand how impractical that scenario is, there are thousands of precise chemical reactions needed to sustain life involving thousands of compounds with varying reactive potentials. Without life these compounds cannot remain in close proximity without destroying each other, that is with out a multitude of different catalysts containing them.

Darwin Evolution is nearly as simple as most people tend to make it.

[Frank]

Hmmm, I'm not even sure where to start here. I guess at the beginning. I'm sorry, but you are incorrect. We indeed have observed speciation. I would start here if I were you: http://www.talkorigins.org/faqs/faq-speciation.html

Next, dogs. In some way dogs are a bad example, but they bring up a good point. The reason it's a bad example is because most all of the changes from wolves to dogs has been directly controlled by humans. Humans were not intending to change wolves into a different species, instead the goal was to breed particular desirable or useful traits into the dog. On the other hand, it's an interesting example because during this breeding process a funny thing happened. One of the precursors to speciation is the physical impossibility of a member of a species to breed with another member of the same species. An example of this would be a male great dane and a female chihuahua. So genetically they can still breed, however even though the same species, the unintentional result of this manipulation by humans has been some splitting of this species. The longer they go without breeding with each other, the further the split will become both physically and genetically.

Next, I need to correct an incorrect assumption on your part. Darwinian Evolution has absolutely nothing to do with the beginnings of life, it only discusses the reasons for the vast number of species. The book is called "On the Origin of Species", not "On the Origin of Life". The study of the beginnings of organic life is called Abiogenesis. So, evolution itself has no bearing on any options of life beginnings what-so-ever.

But to get to your point, the option of life from non-life is indeed correct. You just need to step back and look at it one step at a time instead of thinking that some fully functional cell is suddenly crawling out of the ooze. It starts as a much simpler process. Inorganic matter such as carbon and oxygen react to form amino acids, these amino acids are the building blocks of life. The problem with the ID argument is that it really answers nothing, it only sticks an unknown in to the answer which actually makes the answer useless. To truly answer the question you would then need to explain where this intelligent creator came from. And indeed, it smells more like indoctrination into religion rather than a scientific theory that presents actual evidence to back up it's conclusions. The ID crowd does not gain credibility by attempting to discredit evolution. Even if evolution is 100% wrong, ID still needs to present evidence that they are correct. They are not at all correct by default. This is truly the problem with ID, at least as far as science goes.

[American Muse]

Where do Dr. Evans and his fellow researchers come up with this loony balderdash?

An elephant may live for about 60 years. If elephants reproduce, say, at 10 years of age (a generation), then 24 million generations would take 240 million years, going back to the time of the great Permian Mass Extinction. That was long before mammals (let alone the proximate ancestors of elephants) appeared on the planet.

[Aparate foto]

Humans evolved in the last 250 thousand years, but what drives this changes at a genetic level, what mechanism determines the positive result of a mutation, and what mechanism decide to keep the mutation.

In humans certain body parts have become larger just to attract a mate but in other primates the same organs are smaller but they still work in the same way and get the job done.

How can our brain influence our genetic code so that it can increase the next generation attractiveness?

[David]

Mouse to Elephant? Just Add Time
http://crev.info/2012/01/mouse-to-elephant-just-add-time/

[steroids]

surely you have submitted an academic paper on your hypothesis that has supporting evidence and is ready for peer-review? I mean, to make an assertion as you have, you must certainly have evidence that no one has ever seen before! Put up or shut up!