hello and welcome to more or less on the b. b. c. world service with a programme that sidles up to statistics buys them a drink and ask them where they're from and i'm tim harford as you know we're lucky to have lots of listeners and a proprietary more or less algorithm has determined that eighty seven point three percent of them are loyal seven point three percent lackadaisical and five point four percent crafty we received an email from one of the loyal ones paul dear more or less can you help me unravel an apparent inconsistency between how percentages of human d.n.a. in other species are reported fact one humans and chimps share ninety six percent of their d.n.a. no surprise they're back to at least twenty per cent of neanderthal d.n.a. is in humans how are these two facts reconciled to help with the befuddled aren't we need to define what d.n.a. actually is do you know full name dioxin bye bye nucleic acid found in the chromosomes in the cells of living things d.n.a. determines the functions of each cell and is responsible for characteristics such as eye colour hair colour jean jean is a string of d.n.a. and is also related to a certain trade like having blue eyes genome genome is an organism complete set of d.n.a. which encompasses all its genes if each little piece of d.n.a. is a bit like letters the jeans are a bit like sentences made up of those letters the genome itself is the entire book for any given individual an instruction manual made up of those sentences when we say as national geographic did in two thousand five that humans share ninety six percent of their d.n.a. with chimps are we climbing are we saying it's all the same letters are we saying you can read many of the same sentences in a human book in the chimp book so we spoke to peter donnelly professor statistical science and former director of the welcome centre in oxford in the u.k. he helped us unravel headline he started with the letters the information d.n.a. is determined by the order of the different chemicals that make up d.n.a. and therefore possible chemicals start with the letters a. g. c. and t. kind of think about an hour instruction manual as a long set of instructions written alphabet with four different letters scientists then go through the genome that's the entire book for any individual look jeans these jeans remember like sentences they're specific identifiable sequences of the base letters g. g. g. g. g. g. g. gently in humans and chimpanzees that d.n.a. instruction manual is about three billion letters long chimpanzees are the closest living relative to modern humans professor only told us that humans and chimps separated from a shared common ancestors between six and ten million years ago and this is relevant because roughly speaking the longer two species have been separate the more differences will accrue between their d.n.a. and there are obvious differences no matter how good your teenage self thought some of the apes in planet of the apes looked we aren't the same species however genetically speaking we don't seem to be that different national geographic article citing research by the chimpanzee sequencing analysis consortium claimed that we share ninety six percent of our d.n.a. with chimpanzees professor donnelly says that's right if we compare the genomes of a modern human without chimpanzee they're about ninety six percent similar so if you take a chimp the instruction manual for chimps and human genome the instruction manual for human you write out all the sentences in them ninety six percent of those sentences are going to be recognisably similar but not identical if you just focus on them you imagined writing them out there to d.n.a. sequences would disagree on average about twelve positions per thousand that's one point two percent overall so those are the ninety six percent that are similar and then there were four per cent of the sequences that are completely different let's compare a bit of chimp d.n.a. and a bit of human d.n.a. that sound similar if human piece of d.n.a. red during the two to g. g. gently there a attempt d.n.a. red there if you ever lap come ere you can hear they do sound rather similar however remember a four per cent of our sequences that don't match at all now to the second time this came from the website live science and stated that at least twenty per cent of neanderthal d.n.a. is in humans but how can that be true we have less neanderthal d.n.a. than we do chimp d.n.a. back to professor donnelly neanderthals a branch of the human lineage which separated from our ancestors the ancestors of modern humans something like four hundred or five hundred thousand years ago so by peter dolly's earlier rule of thumb longer two species have been separate more differences you should see in their d.n.a. has been split from neanderthals much more recently than from chimps we must have more than ninety six percent of our d.n.a. sequences are similar the trouble is it's not easy to compare human to neanderthal d.n.a. we have chimps wandering around so we can examine their d.n.a. but we don't have any neanderthals running around can search your own obvious joke here if you like then in december twenty thirteen a female neanderthal bone fragment was found in the altai mountains in siberia it contained a high coverage which means the genome in which most of the information is intact this allowed scientists to work out that ninety nine point seven percent of all human genes remember those like sentences are similar to the genes neanderthals and as you'd expect that beats the ninety six percent figure that is twenty percent number plants actually talking about something different and more about that in a moment the scientists made an even more interesting discovery about modern humans of non african ethnicity left africa about eighty thousand years ago we don't know too much but we know some of the details we learnt recently and initially somewhat surprisingly that that group interbred with neanderthals we know that because we can see the impact of that in modern d.n.a. if you one sequence about the other they great most positions you only see differences about three places per thousand so point three percent because the group are modern humans left africa bread with neanderthals all people that ancestry have chunks of the neanderthal d.n.a. that basically identical in a book analogy would be like long plagiarised passages in total those passages are two to three per cent of the human genome the rest of their d.n.a. the other ninety seven ninety eight per cent is similar but not identical so to come back to our loyal listener paul's question is a ninety six percent overlap between chimps and humans that overlap describes similar genes once we start looking at others neanderthals were starting to ask questions about identical genes similar genes are like two sentences that have a couple of words that are different identical genes like two sentences that are the same text for text all humans share ninety six percent d.n.a. that's similar to chimps air modern humans have european or asian ancestry have on average two to three per cent not have similar but of identical neanderthal d.n.a. within their genomes what about this claim that modern humans carry twenty percent of neanderthal d.n.a. well everyone of asian or european ancestry has a snippet of neanderthal a couple of per cent but the different snippets if you got together a group of them you'll be able to piece together about twenty percent of a neanderthal genome from the snippets that each of them was carrying around take a paragraph here from this modern human or a passage from that modern humans and between them you can assemble about twenty percent of the big book of neanderthal that is all we have time for this week many thanks to professor peter donnelly and if you spot a suspicious that nonsensical number get in touch more or less at b. b. c. dot c.o. dot u.k. producer was lizzie mcneil i am genetically physically and functionally tim harford goodbye more or less was presented by me tim harford produced by lizzie mcneil and made to sound beautiful by neil churchill