How have genetics and developmental biology influenced evolutionary theory?

Sorry I was being lazy and used the picture I could find- I've seen the actual (pickled) embryos of different species. My bad! I do have to be more careful, I know exctly what you mean you can get something slightly wrong and people will hold it against you for years. Did you watch the programme on the developement of the dog, dolphin and elephant embyos? It was in the UK so you might not have seen it, it was very cool though. They used ultrasound to reconstruct CGI picture if I remember correctly.

Not your bad. It's a lovely image. But I just wanted to warn you so wouldn't draw fire for a relatively trivial reason. I have not seen the dog, dolphin, elephant embryos. I would love to see them. I worked in an embryology lab for a couple of years and became really enamored of development...

OG, Your account of what's happening in the cattle breeding industry is fascinating and your analysis makes perfect sense to me. I'm a bit diffident about even offering an opinion, since you are the expert, but I see what you mean about there being two different approaches to solving the problem, the genetic and the developmental. I agree it's totally solvable.

I guess in terms of applying selective pressure, my first question would be how much genetic variation is left? Are the animals highly inbred? Or is there still a lot of heterogeneity left? If more, that's great. If less, you might find it harder to select for the kind of robustness you want unless you outbreed. Or is out-breeding acceptable? I don't know what kinds of constraints you are operating under.

As for phenotypic plasticitythe ability of the animal to develop depending on conditionsthats something you could work with immediately if they are capable of a plastic response. Or at least look for it. Is there any sign of that? Do some cattle do much better than others? I am assuming you would be looking for husbandry techniques, for both the mothers and the calves, that would produce adults better able to live on lower-quality feed. Is that right?

As for your not knowing much, you have totally misrepresented yourself...as I suspected. You might recall that when Darwin was trying to figure out how selection could work to produce evolution, it was to animal breeders that he turned for information and ideas. They educated him.

[quote=asking]I guess in terms of applying selective pressure, my first question would be how much genetic variation is left? Are the animals highly inbred? Or is there still a lot of heterogeneity left? If more, that

Economics and ecology use many of the same concepts, just different language and culture, so it should be a comparatively short learning curve. The currency in ecology is (of course) energy. It's not for nothing they both start with "eco"...

Yes, there is a lot of really interesting research and innovation going on in rangeland ecology these days. In the past, too many "environmentalists" had a shallow and dangerously naive view of semi-desert rangeland ecosystems. They saw most problems as the result of "overgrazing" and their solution was to remove all grazing animals. Much like foresters who advocated total fire suppression. The point they missed is that both grazing and fire were and are and must remain critical formative processes in that ecosystem. If you completely remove either or both of them, what you get is not in any sense of the word, "natural".

The key ingredient that makes both fire and grazing constructive and health-promoting processes is that they happen intermittently. The alternation between relatively brief episodes of radical disturbance, followed by relatively long periods of rest and recovery is the fundamental rhythm that promotes diversity, vitality, and resilience in these ecosystems. While there is no doubt at all that continuous grazing is harmful to ecosystem health, it is equally certain that continuous fire suppression or total cessation of grazing is just as harmful, and for the same reason.

The link to animal husbandry and genetic selection seems clear to me. EVERY biological system--from a cell, to an organ, to an organism, to a herd, to an ecosystem--NEEDS alternation between times of ease and plenty and times of stress and shortage to keep the adaptive capabilities sharp and functioning. An industrial model that seeks to reduce all variation, prevent all stress, and provide ideal conditions at all times is simply not the right tool for the job. It's a great model for manufacturing interchangeable machine parts, but not for producing healthy herds or healthy ecosystems.

OK, now I need to get off my soapbox. Great discussion. Keep it going.

This reminds me of an ecological concept that I learned in college--which is "patchiness" in both space and time. In those days, patchy environments were associated with lots of diversity and a fair amount of ecosystem stability, but I don't think they completely understood why patchiness was good. Nowadays, the view is that --if you view an area as having good habitat and marginal habitat--populations can live in both during good times. The good habitat is operating as "sources" and the marginal habitat as "sinks." When populations in the sinks go extinct, they can be repopulated by individuals from the sources. You can make this idea more sophisticated by considering that what's a source in this 1000 year period my turn out to be a sink in another. So you can think of patchiness or environmental heterogeneity as happening in both time and space.

Just the other day, I was reading about the the ecology of diet (in a book) and the writer was arguing that actual selection pressure occurs not in the sources, where organisms reproduce with little adversity, but in the sinks, where, of course, conditions are harsh and not everyone survives. The result is that over time the population becomes increasingly adapted to the marginal habitat. I'm still struggling with these ideas, so it's probably not very clear... But I think it relates to what you are talking about.

One example, I read somewhere else, was that gorillas mostly eat fruit, but they are adapted to eating bamboo and other plants (tough, fibrous shoots and leaves) because that's what they have to eat when they can't get fruit. Fruit doesn't require speciallized adaptations particularly because it's relatively easy to process and high in calories and nutrients. But even though gorillas are restricted to bamboo and other grasses and leaves at only a limited number of days per year, THAT's where the selection pressure comes from. So their adaptations to eating bamboo don't interfere with their ability to eat fruit when it's available. That seems like a good model for you to consider.

Anyway, to get back to sinks and sources, intermittent grazing is a kind of sink in time (from the perspective of the forage/grass), where adapation to grazing takes place. It also of course changes the vegetation, preventing succession, which is good for grazers. Allowing the forage to recover is an obvious good for the grazers. And I suppose there must be 10 other things I haven't thought of...

I know a fair amount about why fire suppression is bad. (I live in a tinder box canyon, among other things.) But why is total suppression of grazing bad? I don't doubt it, but I'm interested in hearing your (10) reasons.

And I haven't forgotten that we were talking about what some might view as Lamarckism, possibly even Lamarck might think so...

ASIDE: Also, after reading one of your posts, it crossed my mind that some might consider this discussion as sounding like Lysenkoism, and might therefore dismiss it. Do you know Lysenko (1898-1976)? He believed, for example, that Soviet wheat could be made to grow in cold Siberia just by stressing it. He didn't believe in genetics at all and he and his political mentor Stalin basically killed off an entire generation of Soviet geneticists, including some very good ones (not to mention some excellent strains of wheat!). So in the west, biologists have a very strong reaction against any hint of his ideas. It's more than a reaction to a bad idea....Good to avoid sounding like Lysenko. He was also wrong.

If you have a particular environment that you want a population to be adapted TO, I guess that would be true. But I tend to view the environment as constantly changing in time and space and at different levels of scale. So in Time, you see changes from hour to hour, over days, and seasons, but also over periods of thousands or tens of thousands etc, millions of years. Same for geographic patchiness--this creek bed, vs that hill top, this Mississippi Valley drainage vs that Continental Divide. And then time and space can interact with one another, too. In that view, alternation between times of ease and plenty and harsh selection just IS, it's not something that organisms "need." Selection is an inevitable consequence of the tendency of organisms to breed beyond the carrying capacity of ANY environment. (No exceptions.)

But if you want something very specific--cattle adapted to a particular habitat--then I suppose that argument would make sense. So I guess that in ecological terms, your business would be considered a source and your customers would be sinks, where the actual selection occurs. The problem is that no cattle are coming back to you carrying the right genes for surviving in the marginal sink habitat. I'm probably not helping... Sorry. But it's interesting to think about.

I asked earlier if you see any sign of a plastic response in your animals and I'm not sure I understood your answer. Have you actually tried raising calves on some proportion of lower quality food to see if they can grow up to be able to digest lower quality food than calves raised on "the best" food? I know that'd be an expensive experiment. Really, your customers are doing the experiment for you. It seems like that's where you'd find your answers, by talking to them...

Because, there's no way to know in advance if it's possible to raise the same cattle (genotypically) to do better on worse food. Also, you can't know Which intervention would produce that hypothetical result. Would it be feeding worse food to mothers and calves? Or would it be something completely unexpected, like a cortisol spike on a certain day of development? This isn't something that's necessarily going to be intuitively obvious (although you might get lucky).

Ok. Off MY soapbox...

This is getting really good, because it's making me think, and read, and question some things that I thought I understood. I love it.

I checked out Ridley and some of his reviewers. Here's an interview Edge: A TALK WITH MATT RIDLEY that might interest you if you haven't already seen it. He's plugging his new book Nature Via Nurture: Genes, Experience, and What Makes Us Human. Have you read it?

The most interesting thing I've found googling around the web is K.Kull - Outlines for a post-Darwinian biology. I'm only about halfway through it, and finding it pretty tough slogging in places since I'm not that familiar with some of the terms, and mostly ignorant of the history, but it's fascinating. I'd be most interested in your take on it. Here's a little sample to whet your appetite:

So, asking, your question about plasticity is exactly the right one, I think, and the answer is yes, there is a great deal of plasticity in the way different animals respond to selection pressure.
Well, not prohibitively expensive, actually. Of course, what we're doing isn't quite a scientific experiment, since we don't have a "true" control group, but the prevalence of the idea that "nutritional stress is always bad and must be avoided at all costs" among our competitors in the seedstock business does provide a basis for making some comparisons.

For example, we develop our calves on a relatively low-energy diet over their first winter of life (8-12 months of age), during which time they gain only about a pound a day, sometimes less. Common practice is to feed weaned calves for a gain of 2-2.5 lb/day. However, by the time our heifers are exposed to the bull for the first time at 15 months of age, they have been on lush spring grass for at least two months, during which time they typically gain 2.5-3 lb/day. We calve in April and May (which means breed in July and August), which also diverges from the more typical practice of calving in February and March. Under that scenario, when breeding begins in May, they haven't had much time to benefit from the spring flush of forage growth, which in most years doesn't really come until May and June.

Our first-service conception rate is usually between 70% and 80%, whereas for heifers developed on a higher-energy diet 80% to 90% is probably more typical. We feel this is quite acceptable, because our feed cost per pregnancy is probably less than half what it would be for a high-gain scenario. Even more important though, to get that extra 10% bred, we'd have to feed all of them, including the 75% that don't need it, and still wouldn't know which were the less-efficient ones--at least not until they fail to breed back as 3- or 4-year-olds. The basic strategy is to set the bar pretty high at the beginning, believing that those that manage to clear it have a much better chance of being reproductively successful for a long time.
Well, not entirely, because we keep all our heifers and give them a chance to breed, and the female progeny (we suppose) have a lot more influence on reproductive success than the male side. Only about a third of the bull calves make it through the selection process and get offered for sale as breeding bulls.

Not that the male side is completely out of the loop when it comes to reproductive success, of course. One reason our customers choose our bulls rather than more conventionally-raised ones is that they think their daughters are more likely to make efficient, fertile cows. Another is that our bulls have more stamina, durability, heat tolerance, libido, and other strengths that make them able to breed more cows in a shorter period of time.

There are several other things you both have mentioned that I hope to respond to, but haven't had the time yet. Having to do some reading, and actually think about it means it takes longer, but I guess it's worth it. Thanks so much for taking the trouble to do this discussion. I'm finding it exceedingly useful and interesting.

Um no. It's just me spouting off. But I know what I'm talking about (sometimes), and I sometimes write books. Maybe I should write one about this?

I don't know much about alzheimers. I assume though that if it's not a straight genetic disease (like Huntington's, where you get one gene and you can be almost certain of getting the disease), then environment would affect things like when you get it and how seriously. I keep reading that people who live certain life styles are more or less likely to get alzheimers. That suggests that environment plays a role in alzheimers.

By the way, you will often see magazines and newspapers say something like, this disease (whatever disease) "runs in families, so we know it's genetic." But that's illogical. Just because a parent and child have the same problem doesn't mean it's genetic. Obesity is a good example. It also runs in families because of life style choices. Culture runs in families too, whether religion or eating habits. So knowing that a disease runs in families actually tells you nothing.

Asking

What you are asking about is gene therapy where a piece of foreign DNA is inserted into cells in order to be expressed. We are a long way away from this currently.

Most research into this area is being done with very simple genetic disorders for example Cystic Fibrosis . It is caused (in most cases) by a single amino acid mutation in an ion channel. Amino acids are the building blocks of proteins like ion channels- you get an important block wrong and it doesn't form properly or behave properly.

If you just have to replace one gene it should be easy. We do it in simple organisms like yeast and e. Coli all the time turning them into mini factories to make what we want. However because people are large multicellular creatures it can be very difficult.

The main problems are:
Targeting- how to get the gene into the cell?
Rejection- the body is designed to get rid of foreign DNA most of which comes from viruses.
Overexpression- sometimes you can get over the first two problems and then have too much DNA in the cell, which can cause it to make too much protein.
Retention- sometimes everything goes well but after a few days the DNA just gets degraded or the cells are short lived and die. This seems to be the main problem with CF at the moment.
Cancers and immune responses

Developing gene therapies is a very complex business- I have no doubt that one day it will be used to treat diseases. However due to multiple problems that can happen and the fact patients treated by it at the moment have suffered from vast immune responses, organ failure and death, I think it will be a long time before such treatment is widely available.

Don't despair at the HIV front though there is some brilliant research going into preventing it and minimising its effects.