Laurence Hurst (Educator)
I am the Professor of Evolutionary Genetics at The University of Bath. I have won prizes for both teaching and research. I especially enjoy giving talks in schools.
Location Bath, UK
Activity
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See my answer - hope this helps
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Dear Jacqueline, mutations start out rare (low frequency) but can increase in frequency. While there exists the new mutation and the original form then there will be variation with a population. If however the new mutation becomes the version all individuals have then it will be a fixed difference. If we compare this species to another species in which the...
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My pleasure
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If a mutation occurs in junk it is still a mutation, but likely to be a neutral mutation - one with no effects on fitness. I hope that helps. @DrusillaWinters
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I am glad you are enjoying it!
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Regarding data sharing, all sequence data that evolutionary biologists generate is freely available in worldwide resources such as NCBI. It is standard practice to release the information the second it is generated or when the first scientific paper on the subject is published. I pay to have DNA sequenced but never to access deposited data.
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Laurence Hurst (Educator) replied to Geoff Hoppe
One notion of a species is the "biological species concept" that emphasises the lack of interbreeding. In fruit flies (well studied in terms of speciation), the first genetic changes cause only partial hybrid breakdown - in the "hybrids" the males are more affected than the females. And naturally we have no idea about reproduction between fossil "species" -...
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Laurence Hurst (Educator) replied to Jon Bird
@JonBird Notice also that not all evolution is owing to selection - as we saw in the introductory sessions, most sequence evolution in the human genome is likely to be neutral or effectively neutral.
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Laurence Hurst (Educator) replied to Jon Bird
There is evidence from the Framingham heart study data for ongoing natural selection in humans. There is evidence for selection on cholesterol metabolism and blood pressure, both of which may relate to present day diets.
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We do tend to use standard units. We tend to write in powers as well. The convention when we can't write a power properly is to use the ^ symbol i.e. 4.5 x 10^9 is the age of the earth in years. The units we use tend to go with the question. Depending on the discussion we often calculate in tens of thousands of years (out of Africa ~ 80 thousand), millions...
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There is no one number but in part that is because speciation can occur by many mechanisms. In plants changes in chromosome number lead to new species instantaneously - new plant species pop up by this mechanism in real time (there is for example one being traced in North Wales which seems to date to the late 1960s if I recall). Conversely, knowledge of...
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If I understand you correctly, I think you are talking about convergent evolution - the same or similar "answer", derived independently. If so then yes, there are loads of examples. An eye-like structure has evolved multiple times - ours is like the octopus simple eye but theirs is actually better as it doesn't have a central blind spot. Insects evolved a...
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There are indeed different ways of asking how common two strings of anything are, DNA being an example. One question is to ask, assuming a position in DNA aligns between two species, what is the probability that the bases are the same. The second is to ask, if I pick a random base pair in one species, what is the probability it will align with a base in the...
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Wafa - the soot deposits didn't make the new mutations. Rather the soot provided the conditions favouring a mutation if it occurred (or already existed).
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Why we often discuss the peppered moth data is that Kettlewell actually studied the process of selection in action - he put out his moth trap and recorded the rates of the black and white versions of the moth over many years and was lucky enough to see dramatic changes - note these are different forms of individuals in the same species, not different species...
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For the purposes of evolutionary change we just consider mutations that can be transmitted - ie those in germline @JonBird
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@JonBird Any mutation inherited and seen in the fertilised egg - which is just a single cell with one copy of each chromosome from mum and one from dad - will be seen in all subsequent cells be they somatic or germline. Any mutations not so inherited will be particular to that individual but can be transmitted to offspring if the mutation occurs of germline...
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Laurence Hurst (Educator) replied to Hugo Rojas
Some have - am I am delighted to say that some have and have understood the logical inevitability that DNA->mutation-> changes in mutation frequency and have jettisoned their old beliefs.
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Many plants survived the recent ice age in so called "refugia". As the temperature warmed up they slowly spread towards the poles as the ice retreated. No doubt some seeds and microorganisms persisted also under the ice (microorganisms have an amazing ability to persist), but for the most part the trends we see are of species recolonising from the refugia as...
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With our new genetic tools we can indeed now see evolution happening in real time - Darwin never could.
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Caterpillars are by definition the stage prior to butterflies and moths - so if you known the number of these you know the number of species with caterpillars.
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Dear Jon, as it happens the expert on these moths (Mike Majerus) was the best many at my wedding. I've never seen anyone seriously questioning the data from Kettlewell. The coupling to the blackening of the trees seems very well resolved. There is a replicate experiment going on in Eastern Europe at present as there the trees remain dark - and the moths...
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the strength of selection is indeed dependent on the extent of differential survival.
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The environment doesn't cause the mutation. Mutations happen all the time in all genes. Occasionally these are beneficial in the new environment. To see the difference consider this analogy. I move to a country where the petrol for my car is slightly different. I could work out what the problem is, go into the engine fix the one bit that needs fixing and...
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Dear Jon, To a first approximation of the allele is neutral it stands a 50:50 chance of going up or down in frequency. The other question we ask is what is the probability it will by chance go from rare (one copy only) to being so common everyone has the new version. This probability is 1/2N, where N is the number of individuals in the population. As the...
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Wafa - we share a common ancestor with all other species. Our common ancestor with chimps we think was about 6 million years ago. It was neither chimp nor human as neither then existed. Our common ancestor with mice was about 100 million years ago and was neither mouse nor human.
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Dear John, For multicellular species like us (but not like plants), we divide our cells in the embryo into those that will make up the body (soma) and those that will be so called germline - the cells that will go on to makes eggs and sperm. Only mutations that happen in the germline cells and their progenitors will be transmitted to sons and daughters. So...
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Dear John, These questions are more in the land of chemistry than biology. But we know a few things - RNAs (single strand of nucleic acid - like one half of the ladder) tend to bend back on themselves and make so called "stem-loop" structures. You get mutual base pairing in the stem parts of the structures. So base-pairing per se is probably just a chemical...
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Laurence Hurst (Educator) replied to Lorraine Hamer
Dear Lorraine, the idea for the course was to support teachers at all levels but also pupils at secondary/High school and above. You are right that this level is too high for primary students.
We have produced full lessons and all resources for teachers of year 6 (10-11 year olds) that you can find...
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Dear Clemence - the idea for the course was to support teachers at all levels but also pupils at secondary/High school and above. You are right that this level is too high for primary students.
We have produced full lessons and all resources for teachers of year 6 (10-11 year olds) that you can find...
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Most mutations are indeed bad for us, but a few can be advantageous - see the section on selection and adaptation
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@WafaAbdelkreem Indeed - because of the nature of DNA, mutations are transmitted well from parents to offspring and then on to their offspring.
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Dear Wafa, It is important to distinguish "physiological adaptation" and "genetic adaptation". If I simply move to higher altitude or somewhere cold my body adjusts its physiology. This can include making more or fewer red blood cells. This is physiological adaptation. This is not evolutionary or genetical change - the raised levels of red blood cells will...
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Laurence Hurst (Educator) replied to Andy Hurley
Organisms are responding to life it cities. Can you see this article?
https://www.nationalgeographic.com/news/2018/05/urban-living-drives-evolution-in-surprising-way/
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Epigenetics refers to variation that is explained by changes to the DNA that aren't owing to the sort of mutation we have looked at. For example, a C in DNA can have another chemical group - a methyl group - attached to it. If this occurs sometimes it stops a gene from turning on. So differences between genetically identical cells in your body are often...
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It depends on what you mean by "cause'. We know the genetic basis of the white and black forms - it is indeed two different versions of the same gene (and if you have both the black and the white version of the gene the moth is black - we say black is "dominant" over white. However, this just defines two different types. If you want to know why one is more...
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In short the strength of selection is dependent on the extent of differential survival in the population associated with the trait. Lets go to a case of black moths/mice on a black background versus a white version on the same background. You can imagine a case where there are very few predators about - if so the advantage of being camouflaged is small and...
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Indeed, the movement of species around the globe often causes major effects when the invading species take over.
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The simple answer is yes. One of the first breakthroughs in this regard was the discovery of the genetic basis of how organisms behave over the 24 hours of the day. Mutations in the period gene in flies were showed to be inherit and affect how different flies behave differently. Twin studies in humans show a genetic component to many behaviours e.g....
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Continue!
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Dear Wafa
Just bear with the genetics. If you understand DNA you will understand how evolution works. Let me know if you have any issues. -
Our resources are here. They are made for year 6 and work very well during in school tests:
https://people.bath.ac.uk/bssldh/LaurenceDHurst/Outreach.html
I'd be interested to hear your thoughts.
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Dear Lorraine
Our resources have been extensively tested with year 6 pupils (more than 3000 students). We find that all students (regardless of ability) responded really well with large improvements in understanding. The resources are here.https://people.bath.ac.uk/bssldh/LaurenceDHurst/Outreach.html
I'd be interested to hear your thoughts: -
Dear Katherine, The course is based on our trials of how to teach evolution - we showed that teaching genetics before evolution is a really good approach :
https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2002255This explains the structure of the course and of the resources that we provide for primary schools....
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Dear Sarah, Our lesson plans with all associated resources, for year 6 - fully tested using a large randomised control trial - can be found here:
https://people.bath.ac.uk/bssldh/LaurenceDHurst/Outreach.html
I'd be interested to hear what you think of them.
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Dear Sara
We have fully documented lesson plans for year 6 that have been tested using a very large randomised controlled trial - the two we recommend passed with flying colours. Further reading, homework and all lessons plans are available here (see bottom of the page):https://people.bath.ac.uk/bssldh/LaurenceDHurst/Outreach.html
Let me know if you... -
Whether the mutation that is favoured was already present at low frequencies or appears by mutation after the selective pressure (but not because of the selection) is hard to say in many cases but also does not decide whether this is selection or not.
As it happens the black form is favoured in some parts of Eastern Europe where some trees have very...
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For any given mutation subtle effects are very hard to know about. However for groups of the same sort of mutations (e.g. those that are distant in the DNA from genes) the neutral theory makes predictions about their collective properties, such as the relative numbers at different frequencies).
There is a very large body of ideas - called the “nearly...
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Neutral mutations don't cause new species but can become a difference in the DNA between two species. Imagine a population splits in two: one half moves off to the east the other off to the west to never meet again. The two populations will accumulate their own unique sets of neutral changes. Over time these mutations accumulate and the DNA of the two...
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When we do things in such a targeted manner they are not "natural selection'. Anthropogenically influenced natural selection is a good way to capture much that is happening. Another effect we are having is that, owing to global trade and movement we are relocating species by accident (e.g. in cargo).
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mismatch repair enzymes - not the most original name I grant you
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Currently many species are genetically changing owing to human activity that changes the environment and so causes selection . Fishing for example selects for fish that reproduce earlier. This is still regarding as "natural" selection. There is another process - artificial selection - in which we breed organisms with a very particular property in mind. So...
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Andy, Mendel was aware of Darwin and recent scholarship suggests he was influenced by him. Darwin didn't know Mendel's work. Recent scholarship suggests that even had he been aware it wouldn't have had any major effect on his thinking (Darwin actually discovered Mendel's famous 3:1 ratios independently but never really saw their importance). Neither knew...
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How viable are changes? It depends - some are lethal, many have very little effect is any. Occasionally some changes are beneficial.
The order of As, Cs, Ts and Gs is the information that is transmitted.
Chemically speaking A and G are a bit similar and C and T are quite similar. Indeed a small chemical change can turn a C into a T. A and G belong to...
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Dear John, no the DNA bases are nucleotides not amino acids. The string of nucleotides on the DNA is used to specify in any given "gene" the string of amino acids that define the protein associated with that gene. To do this the DNA is "transcribed" to make a messenger RNA (like one side of the DNA ladder), which is then read by cellular machine called the...
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@SophieS hi Sophie, mutations are not directed. They occur by chance and then a few spread in the population owing to selection.
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Bill - we are here to help. These concepts are pretty abstract and not easy. Just ask if you would like clarification.
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Laurence Hurst (Educator) replied to David López
David - this is a really good point. Some changes to DNA affect phenotype but many don’t - all are evolution if the mutation goes from rare to common.
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It is the nature of errors like this that they are rare. And mutations are incredibly rare - the chance that any given position in DNA will change in any cell division is about one in 100 million! Really rare. But just occasionally the wrong base gets added - there is no law of physics which suggests this to be impossible, just rare. In addition, a chemical...
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I think you have it - when food is abundant people tend to be overweight. This isn’t evolutionary change as it isn’t a genetic change- take the food away and people aren’t overweight. A genetic change is as detailed earlier- mutations in DNA that go from rare in the population to common.
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Selection never acts because it is “good for a species”. We see examples of mutations that are good for individuals but bad for species that are favoured by natural selection. It is only about the fitness of the mutation.
If a species has adapted a new mutation would only affect one individual in the population (new mutations are incredibly rare in any...
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All mutations start out as rare events within a species. The question then is what happens to them over time and why. The why could be chance - otherwise known as drift. By chance they could be eliminated from the population or increase in frequency. If they increase and become common then it will cause a change between species and the sequence will have...
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You should have a look at the literature on Foxp2 -https://en.wikipedia.org/wiki/FOXP2
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Chromosome breakages and fusions are not uncommon over evolutionary time. There need not be any advantage.
Regarding multiple sex chromosomes these tend to mess up meiosis (making sex cells) so tend to lead to infertility. In terms of changes to what folks look like it varies. XXX females can have almost no effects, but some have webbed necks and some...
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Not just any gene - most of our phenotypes are under the influence of many hundreds of genes.
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drift is indeed the other name for the process of random movement of allele/mutation frequencies.
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There certainly is evidence that from having families with Neanderthals our DNA contains remnants of the neanderthal DNA. It varies around the world (zero in Africa), up to 4% elsewhere.
The 8% figure is the usual one given for the proportion that is so called endogenous retrovirus - these are the products of viruses that inserted copies of their DNA into...
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@davewilliams Absolutely - whether mutations are good or bad for you very commonly depend on your environment, whether this is the physical environment or the biological one. For example, the mutation in the gene CCR5 that confers resistance to HIV in humans looks to be bad for you in the absence of HIV.
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Dear Raymond, the mitochondrial DNA is inherited differently. We get nearly all of ours from our mothers. Fathers have it but don't transmit it, even though it powers the sperm.
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Dear David
It does happen but it is very rare. They are called Uniparental disomies.
Uni = one
Parental = from parent
disomy = two chromosomesI actually wrote a paper on them many years ago as it happens:
Hurst, L.D. and McVean, G.T. (1997) Growth effects of uniparental disomies and the conflict theory of genomic imprinting. Trends in Genetics ...
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With pleasure. Inheritance here can mean either from one cell to the next or from parents to offspring. The two are slightly different so I'll look at each in turn. First, cell division. If a cell is a heterozygote at one site in DNA - e.g. T-A pair on one chromosomes and C-G pair on the other (we could abbreviate to being a T-C heterozygote), then because...
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Laurence Hurst (Educator) made a comment
Welcome everyone. I hope to be able to answer questions as we go through the lectures. Don't hesitate to ask and don't hesitate to also ask for clarification if I am still unclear.
I hope you all saw the introductory video on the new role understanding genetics plays in our understanding of evolution. It was, however, rather well hidden so if not you...
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Welcome everyone
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Indeed. We now routinely do evolution experiments in the lab setting but use organisms that reproduce really fast - bacteria or yeasts for example, even fruit flies. You could in principle do the same sort of experiment on slow reproducing species but it would take so much longer.
One of my colleagues has an experimental bacterial system that when put...
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@LeeScott There are at least four mutations that have occurred at different times that enable this. They all have the same effect, to switch on the gene to enable milk sugar digestion after weaning. This evolution is recent - in the last 10,000 years which is the blink of the evolutionary eye. These mutations then increased in frequency in the relevant...
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Indeed, most mutations are bad - making a random change to a well functioning machine will often make it worse. But occasionally we see mutations that do benefit their bearers. We will look at some examples later. But in humans for example, mutations that enable us to digest milk as adults have occurred and been good in some contexts to the bearers. ...
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Laurence Hurst (Educator) replied to Lee Scott
I am delighted to have helped here - often the best courses are those that stitch together the fragments of understanding into a more coherent whole.
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Dear Tony - no surprises is a good thing - it reinforces that your understanding was right all along - this too is great to learn/have confirmed. Thanks for your comments.
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It was our pleasure
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The teacher resources we have devised we did so with budget in mind - none of the resources will cost more than a few pounds for one class. Toilet rolls are just brilliant because they come with perforations that you can use to indicate a certain amount of time. But don't use them outside on a wet day! The washing line of time we also recommend.
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Laurence Hurst (Educator) replied to Lee Scott
I have heard the same argument - but it is still code for condescension - it is as if it is code for "yeh we already know that, what is new?" But I would still question the use of the word "trivial". In common parlance trivial means utterly easy, uninteresting, to be past over so fast because we have moved on.
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I have an inordinate fondness for slime moulds - no joke I was an avid reader of the strange literature on acellular slime moulds as they have unusually large numbers of different sexes (a problem I worked on in my early career). We have been studying the misunderstandings of school children about evolution - that could be an interesting way in. @AmandaOliver
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Laurence Hurst (Educator) replied to Lee Scott
I think I don't agree - for mathematicians "trivial" is a form of condescension- i.e. if you don't see the connection you are soooo stupid. Special isn't the same - it is just a lazy way of saying logically a bit different. @AmandaOliver
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Laurence Hurst (Educator) replied to Jim Hill
I'm not sure I'm needed here as you have all well answered the question. In short the bleaching would not affect the germline (sperm and eggs) and so the next generation's skin colour would be no different from the present generation's.
As regards epigenetics (irrelevant for skin bleaching, but relevant in the more general context of environmental induced... -
The inaccessible versions I presume to be the ones I struggle/fail to understand! @AmandaOliver
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Laurence Hurst (Educator) replied to Lee Scott
Hi Amanda - when Darwin considered sexual selection he counterposed it to natural selection. This is what I meant by "special". Special= different. It wasn't a reference to the thread. Now we think it more as a different class of natural selection, but still worthy of its own name.
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John - I don't know the answer but I like how your brain works. It is just these sorts of strange sideways view questions that have kept folks interested, engaged and intrigued. What I can say is the funny shaped eggs of some cliff dwelling birds seem to be adaptations to prevents the eggs from rolling off narrow cliff edges. Nothing to do with grapes, but...
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Could we have done more to help engage from the outset? @ShirleyMitchell
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Dear John and Lee - it is so wonderful to hear that there are folks wanting to hear about evolution and how it works. Our mission at The Milner Centre is to bring our research and the current state of evolution to folks who want to be engaged. @LeeScott
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Laurence Hurst (Educator) replied to Lee Scott
Amanda - yes indeed, sexual selection is an important process. Darwin considered that strange sexual ornaments that seem to hinder an individual (think big tails of a peacock) require a special explanation. And depending on what you mean by special he was right. But some argue that if females have a preference for long tails, then as far as males are...
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I couldn't find an accessible more recent overview that is open access - I'll keep hunting.
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protein - a polymer (string) of "amino acids". We use 20 different amino acids. The order of amino acids in a given protein is dictated by the DNA code in any given gene. Proteins differ in length and in the order of amino acids. Commonly known ones include haemoglobin in blood. Our enzymes to convert one chemical to another are proteins. Egg white is one...
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species - this will need an essay on its own. Biological species concept consider two species as distinct if mutations in one cannot enter the gene pool of the other.
But useless for extinct species and asexual groups. Other notions look to the phenotypic space between groups being unfilled: fossils can be considered as distinct if they are not part of a... -
thanks that is helpful - these are funny terms
phenotype - what an organism is - what it looks like, how it behaves etc. Your size, weight, hair colour, eye colour are simple ones. But also when you die, your loves, hates, passions and phobias, how long you sleep at night, your blood pressure, cholesterol level - any fact about you is a phenotype and the... -
Hi Amanda I think this might be an approachable (correct me if I am wrong) and open access account of relaxed clock methods:
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Laurence Hurst (Educator) replied to Jack Gray
Dear all - we are here to help. The problem with science is that no one can ever guarantee that the correct answer is an easy to understand answer. Why should it be? Credit to anyone prepared to push themselves outside of their comfort zone. It is an adventure that is worth it. @TonyLo
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Laurence Hurst (Educator) replied to Lon Brouse
@IanPerkins Hi Ian - I am very interested in this comment. I was always taught that to teach complex ideas like HGT it is best to build up from a simple model, establish that and then add complexity. Chemists for example start with simple Bohr models of atoms, build up to more complex ones (probability density functions for elections), then go to quantum...
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Laurence Hurst (Educator) replied to Lon Brouse
Aoife is one of my best mates - we have done some fun work together. She is great. And yes, duplication is important for many species as a source of novelty. But a duplication is just a gain of DNA and can be treated like any new mutation. @LynnWilhelm
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Laurence Hurst (Educator) replied to Lee Scott
Lee - I am with you here. Once you see how DNA works then evolution becomes an inevitability. We are rare humans living in the post DNA age - an age where we understand genetics and in turn evolution is presented to us on a logical plate. But what great brains to see all of this! @LeeScott
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Shirley - thanks for the feedback. It is really interesting to see that engaged smart folks do see the logic in the end. I wonder if we could make the preamble more relevant and easy to engage with as it is presented - any ideas? @ShirleyMitchell
