That statement is false. They might differ in one AA perhaps according to one gene, but certainly not in every gene.

You could answer yes or no in my class – it’s the rationale you give that would be the important part.

But I suspect you’d be well-served by going with "yes," and getting into how related organisms have homologous proteins…

Like all members of the animal kingdom, they must share a distant common ancestor (they both have what is known as eukaryotic cell structure). They’re related in the same sense that all modern animals, plants and fungi are related – very distantly. At some stage in primeval natural history, a single species would have sired both the animals which would evolve into chickens and those which would evolve into horses.

I’m not completely sure, but I’d hazard a guess that the common ancestor would have been a primitive dinosaur. Aves (birds) and mammals are both descended from dinosaurs as far as I know.

Mammals are not descended from dinosaurs but from a family of reptiles that was closely related to the earliest ancestors of the dinosaurs. This would most likely put the common ancestor of chickens and horses in the early Triassic period.

And ultimately, a single individual, yes?

Yes some organisms are closer related to others, BUT keep in mind according to DNA sequences ALL OF US came from A SINGLE ancestor where we over a periods of time diverged.

"In the study of early life on Earth, one name towers above the rest: LUCA. LUCA is not the name of a famous scientist in the field; it is shorthand for Last Universal Common Ancestor, a single cell that lived perhaps 3 or 4 billion years ago, and from which all life has since evolved. Amazingly, every living thing we see around us (and many more that we can only see with the aid of a microscope) is related. As far as we can tell, life on Earth arose only once."

It might be more useful to think about the descent being from a single population rather than a single individual – evolution acts on selection of individuals, but surviving individuals recombine features and the population (kind of as an "average individual") changes over time.

Has it ever been established with certainty that all life on earth descends from a single cell? Isn’t it possible that whatever caused the first life to arise on earth actually gave rise to several organisms, each of which may have led to a different form of life? Or perhaps, through DNA exchange and recombination, every organism that lived on the early earth became our common ancestor? We might not share one common ancestor but several.

yea, your point makes sense as well and I consider that a possibility as well. "Has it ever been established with certainty that all life on earth descends from a single cell?" – Alex, virtually nothing in science is established with certainty. The more I learn about biology and evolution the less I know. GOD DAMN, BIOLOGY IS A COMPLEX DISCIPLINE.

(sorry if my english isn’t good)
good question
of course they are related, every organisms are related. but your statement proves nothing but show that these two kind of animal share the same evolution from unicellular to multicellular. besides, it is just one amino acid sequence, it can not prove that horse and chicken are related nearly
here is one of suprising number, the percent of difference between amino acid in hemoglobin in human’s blood and dog’s blood is only 16.3%. nonetheless, never think about that human and dog are related nearly.

only by marriage

Hi,
I personally have a problem with this type of "tracing" of our evolutionary past using DNA. Right from the beginning of the geologic timescale there is a problem if you use this thinking as a means to "prove" evolution. The problem is that the earliest life forms (cyanobacteria, the archaeans, and eukaryota) are genetically speaking completely different. They appear consecutively in the fossil record/geologic time scale and are dated consecutively.

They are so genetically different scientists now use a 5 kingdom system to classify life. Bacteria and archaens are two DIFFERENT kingdoms of classification. Eukaryota contains the two traditional kingdoms of plant and animal along with fungi and protists being another kingdom. I do not know if all scientists recognize the 5 kingdom system, but some do as far back as the 70’s. The point is that they are genetically worlds apart.

Cyanobacteria (found in the Archaean age–supposedly when life first appeared) are found to be the oldest known fossils, found in archaean age rocks from Australia dated at 3.5 billion years old. Cyanobacteria are still alive today (how?–is a question, another issue), so their DNA can be studied.

Archaeans are in the next geologic age (Protereozoic). They are dated at about 1.8 B to 2.5 B, are alive today (how?) and weren’t discovered (alive) until the late 70’s. Here is a quote from the University of Cal. Museum of Paleontology’s website, speaking on the archaeans–"biochemically and genetically, they are as different from bacteria as you are."

Then the eukaryota started appearing about 1.8 billion years ago. They are fungi and protists, but also all flora and fauna in the later protereozoic. Protereozoic goes from 2500M to 543M years ago.

These are all very very diverse genetically and are the beginning of life evolutionarily speaking. If the beginning of life had such genetic diversity and evolved from a common ancestor, then how can someone use genetic resemblance as an argument for evolutionary tracing in DNA. Evolutionary tracing would seem to have no foundation since the so-called first species are kingdoms apart.

Genetic resemblance, one could argue, could be considered evidence of a common designer, especially in light of the afore mentioned information. This info is mainstream evolutionary thought and did not come from creationist literature.

First of all, let me clarify that fungi and protists are not in the same kingdom but two separate kingdoms. That said, as different as various kingdoms are, it would be wrong to say that there are no similarities. Archaeans, for example, share many important traits (the structure of their ribosomes, for example) with eukaryotes. Also consider the evidence for how each domain could’ve evolved from earlier forms (such as the endosymbiotic theory and the RNA world hypothesis), and the conclusions are pretty solid, in my opinion.