It is often cited that humans share 99% (or 98%) of their DNA with chimpanzees.  On the other hand it is stated that siblings share only half of their genes.  What (if any) is the difference between DNA and genes; or, how can the above two claims be reconciled? (I am assuming of course that chimps and humans are more different from each other than two siblings are from each other.)   (I am asking this question as a layperson, who had a little biology in school but not much more.)  June 2015 Addendum: Here is a nice  just released by MinuteEarth; I do not know how accurate this video is, but as a layperson I found it insightful.
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I made an answer on the Scifi.SE that can be read . It is about how the characters in the story Jurassic Park might have gotten DNA for all the species shown.  In my answer, I said this:     Apes and Humans, for example, share over 99% of their genes. That means the difference between our species is less than 1% of our genes. In fact, all life on Earth shares about 50% of it's genes.   but in the original posting (before someone edited it) I chose to use the word DNA instead of genes.  He left this comment in the section to explain the edit:     Sorry, I'm a biologist, I can't help it. Humans and apes share 99% similarity in the coding sequences of their DNA, the ~5% that codes for genes, not on all the DNA. I simplified this to genes for the answer.   I have a basic high school understanding of DNA and genes, so I'm afraid I fail to see the difference between using "DNA" or using "genes" in my statement. I understand that genes are specific sequences of DNA that are used by the cell in some way. I understand that DNA is more generic, including all of the strands, whether they are used or not, whether they seem to code for something or not.  So is it wrong then to say that apes and humans share 99% of their DNA or is it equally correct to say "genes"?
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My question here is about evidence for evolution from Embryology and from Genetics.  Mammals do have similar Embryos, but is it the case that for each species there is an embryonic development that occurs in earlier species, has such relationship been observed? What I mean for example if we generally conceive of having species$Sp_1,Sp_2,...,Sp_n$ where each $ Sp_{i+1}$ being evolved from $Sp_i,$ then is it the case that the embryonic development stages of $ Sp_{i+1}$ contains some of the embryonic development stages of all of its ancestor species.  Similar question to 1 but regarding Genetics, is it the case that every species has a genetic thumbprint of its ancestors that lie there in the non-functional sections of its DNA, i.e. is it the case that all the genetic history of our evolution is recorded in the non-functional section of our DNA. So do human DNA have some portions of the DNA of some dinosaurs for example?
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In some cases two species can hybridize. For example, Tigers and lions can hybridize to produce "".   Would it also be possible for humans and chimpanzees (or any other species) to hybridize ? If not, what would be the likely cause of failure?  Why do some hybridization matings produce offspring, like the Liger, and some not? What mechanisms prevent hybridizations?
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People seem to believe that one's consciousness is a "different" consciousness than that of others, but the "same" consciousness as the one that has been in one's body in the past and the one that will be in one's body in the future. How likely is this to be true and why?   Also, I have almost no knowledge about neuroscience, so please refrain from using neuroscience jargon if feasible.
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I have tried to calculate the relatedness for haplodiploid organisms, but cannot understand the calculations behind full sister and full brother.  (taken from  I have managed to solve the other cases. Since female will have ZZ:  female will share 1/2 of her genes with daughter female will share 1/2 of her genes with son female will share 1/2 of her genes with mother female will share 1/2 of her genes with father  Since male will have only Z:  male will share 1 (100%) of his genes with his daughter male won't share anything with his son (unfertilized eggs leads to male in haplodiploidy system) male will share 1(100%) of his genes with his mother male won't share anything with his father (unfertilized eggs leads to male in haplodiploidy system)  Even though I figured out how others work, I wasn't able to calculate r for fullsister fullbrother? How can it be 3/4,1/4,1/2,1/2?
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What determines speciation at a molecular level?  At what point does a scientist determine two lineages are different enough to be considered separate species?  Does it have a margin of error?
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Most animals look almost identical to their peers. To distinguish lions we record the spots on their face; with whales we look at the blemishes on their tail or flukes. In other words, we have to try hard to distinguish one lion from another.  In the case of dogs, we have created many different looking breeds - but within each breed they look the same: one poodle looks very much like the next one.  On the other hand, with humans we have not only the different races (cf. dog breeds), but even within one race no two people are alike. And, not only are the faces different, the body shapes vary equally much. We use face and body shape (and voice) to recognise each other. Most other animals use smell or sound.  I thought the reason for our uniqueness might be that, with civilisation, we are not constrained us to look the same. However, even in hunter-gatherer tribes each person looks different from every other one.  So what is it in human evolution that made us unique in this regard? And, are we unique? I cannot think of any other species with as much variation as ours, but are there others?
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In short  Looking at the genetic code, it appears that most redundancy is on the third letter rather than on the first or the second letter of the codon. Why has it evolved this way?    Longer version  In order to compare the relative redundancy accounted by each letter of the codon, let's assume that that every codon occurs at equal frequency. It is probably wrong but useful for the sake of the calculations. Using observed frequencies of codon usage in a given population would change the following probabilities but the question of why some positions in the codon has more redundancy than some others still hold.  A substitution of the first letter of the codon has a probability of $\frac{1}{2048}≈0.00005$ (Stop codon) to be synonymous. A substitution of the second letter of the codon has a probability $\frac{3}{256}≈0.012$ (nucleobases U and G) to be synonymous. A substitution of the third letter has a probability of exactly $\frac{2}{3}$ to be synonymous.  Probability of a substitution to be synonymous given that it occurred on the...   First letter: $\frac{1}{2048}≈0.00005$ Second letter: $\frac{3}{256}≈0.012$ Third letter: $\frac{2}{3}$   Why are there more redundancy on the third position than on the second (which has more redundancy than the first position) in the codon?
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To be clear, I'm not doubting that homo sapiens and homo neanderthalensis did interbreed: of that much I'm convinced.   Within the past few years I've seen an upcropping of pop-sci articles discussing the interbreeding between pre-historic species of humans. In everything that I see in these articles, as well as in scientific literature (my college Bio textbook, among others), I see these different humans being referred to as separate species.   This conflicts with my understanding of a species. Given the following definition, wouldn't homo sapiens and homo neanderthalensis be the same species?     A species is often defined as the largest group of organisms where   two hybrids are capable of reproducing fertile offspring, typically   using sexual reproduction.      Is this definition incorrect?  Are the publications using "species" colloquially, as opposed to scientifically?  Is "species" still a poorly defined concept? (see )   Thanks!
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I'm stuck on the following probability problem: parents keep having children until they have one girl, at which point they stop; and babies are girls with probability 0.49. If we select a child uniformly at random (from the entire population of children) what's the probability he or she has exactly one sibling?  If a couple has only $2$ children it means that they had first a boy and then a girl. So why the probability asked is not $0.51 \cdot 0.49$? What I am missing?   It seems that the correct answer is $2 \cdot 0.51 \cdot (0.49)^2$, but I don't know how to get this result. Thanks for your help.
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Brothers and sisters are siblings.  Husbands and wives are spouses.  Mothers and fathers are parents.  Sons and daughters are children.  Grandparents, grandchildren ... but what about uncles and aunts, or nieces and nephews?  In writing this, I scanned the "Similar Questions" sidebar and found that half of my question is already answered; there is no real term for nieces and nephews.  Bummer.  But I'm still wondering about aunts and uncles: does anyone know about that?
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I would like to know if evolution is continuing to happen in modern humans, assuming things like existence of the nuclear family structure, fidelity to one partner, etc. It seems to me the answer would be NO because evolution depends on differential reproductive rates, but in the modern world, all male humans have roughly 2.5 (or whatever the number) kids. Add in the process of culturally modified selection pressure, and it seems to me that even an "unfit" male would end up having a couple of offspring. The fittest male (or female) is no better off than his or her contemporaries because of this "leveling" effect.   However, the impression I get from the popular science media is that scientists think evolution is continuing to happen. I would like to know what the actual scientific consensus is, and why. Thanks.
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In January 2012, David Icke published a book (ISBN: 9780955997334) entitled “Remember where you are and where you come from” in which he challenged what he claimed to be the view of mainstream science that 90–97% of the human genome was , serving no function. He implied, instead, that it must have a function, but that this was unknown.  Is it still true that we do not know what all this DNA does? I see that we consider this DNA to be non-coding, but does that mean it is “junk”? I find it hard to believe that it can serve no function, otherwise why would the DNA be there? Is it possible that it is used for things we don't yet understand?
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I was thinking about something the other day (that is probably stupid), and thought this would be a good place to talk about it.  If someone wanted to draw its family tree over the last 1000 years, he'd write a binary tree with a depth of about 40 (counting 25 years on average between each generations). This tree would have 240 leaves, or about 1012 ancestors on the deeper level. That is obviously much more than the total world population and a stupid figure when you think about it.  The only explanation that I can think of is that a real genealogy tree must have "linked" branches at several levels that change the actual number of ancestors. Anyway, for an average person, how many ancestors would that make? Could one assume that all or nearly all of the persons that lived in its country or world region a 1000 years ago would be part of its ancestors?
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I am not even remotely an expert in this field; I just got curious, so help me.   First of all, let us remove all human sentimental attributes from this question (such as connotations of  or emotional reactions thereof) and ask it from a purely scientific point of view. The typical facial feature of a West/Central African person (the so-called ) exhibits a wide nose, a lack of nasal bridge projection (similar to many Asian noses) and a prognathous skull shape that resembles more closely to our ancestor Homo Heidelbergensis than many other indigenous phenotypes from other parts of the world do.  I agree that this claim sounds anecdotal, and is certainly not true of all Africans (for example, Ethiopians), but one cannot dismiss it simply on grounds of ethical policing. I cannot help but notice that many of my African friends remind me of our shared ancestry (with no disrespect meant whatsoever), as is clear from the photographs below, one of a supposed Homo Heidelbergensis and one of a random African Homo Sapiens of today.     My question is the following. What is the reason behind this seeming resemblance? Is this appearance an illusion and possibly a construct of a prejudiced mind, or does this have a valid scientific answer? For example, are most Africans closer to our ancestors than the rest of humanity is? How does evolution answer this question?  Thank you for your help.
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In the picture below, which I obviously do not own:     it depicts two different phylogenic trees, one which is based on molecular comparisons and another one which is based on body-plan grades. My question is which is more common or accepted in the current Biology world?  Image reference:
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I am wondering if animals do evolve even after birth and gain DNA changes that give them advantages and make them more suitable to the environment while they are alive, then pass these "enhancements" to their children  UPDATE  After all, cell do split and multiply when the animal is alive, and it could end up with a totally different cells than the one born with, so if a mutation happened during this period that led for it to be the dominant "property", what stops it from being passed on? Is there a research on this?