Climate Change: Part 2 How Science Works

Note: This program first aired March 8, 2014.

It’s the nearing the end of winter (we hope), and most of us in North America are sick of the cold, I know I certainly am, and I love winter! Taken in this context, a warmer climate doesn’t sound that bad. Maybe you or some one you know has even questioned how “global warming” (as it is called in the popular literature) can be real if we are having such a cold, hard core winter. Actually, global warming is a misnomer. The warming part refers to the increase in mean or average global surface temperatures, but that is just an average. We can average both 0 plus 10, and 4 plus 6 and get 5 each time. The range between 0 and 10 is much greater than the range between 4 and 6 yet both data pairs tell us the same story when averaged together. Averages are necessary when looking at climate, because climate is a global phenomenon, the result of a global system. The Earth has warmed approximately 0.7 degrees C (or 1.25 degrees F) in the past 100 years. But don’t let the average warming lull you into the dream of the end of winter, while its likely that winters may be getting milder, more heat in the climate system ultimately means more instability, and more chaos in weather patterns. This instability can mean things like what happened this winter, with the polar vortex wandering south, are also likely.

At least if you are questioning the veracity of climate change this winter, you are doing so based on evidence, the evidence being its cold! How can this be a sign of global warming? I applaud you for looking around and actually observing what is happening in the world around you, and making connections to things you have heard are supposed to be happening. The problem is, climate isn’t quite that simple and as a result, we shouldn’t really be calling it global warming. The phenomenon is global in scale, and most of us operate on a human sized scale of observation. So where you are at any give moment (or many many moments this winter), may seem colder than usual, that doesn’t mean that on average, Earth isn’t warming up, it is.

The hardest conversations to have are those with people who don’t “believe” in climate change. Not believing in climate change is sort of like not believing in gravity. Its not believing in how science explains things in the world. Not believing in how science works is always a choice, but people need to understand the implications of that choice. Science seeks to explain natural phenomena through observing, collecting evidence, testing and establishing attribution or cause and effect.

Sometimes science misses the truth because it isn’t asking the right questions, or asking enough questions. That isn’t the case this time around. There are so many scientists working so hard on this issue, from so many different angles; we’re not missing any big picture components. There is so much evidence that has been documented, about how the climate system works, what makes is shift, how it shifts, how fast it shifts. There is a lot we don’t know in this exciting field of inquiry, but the big picture mechanisms of the climate system are well established.

So do me a favor, and when you want to have a conversation about climate change, don’t start it with anything having to do with belief. While there are philosophical discussions to be had about any topic, including climate change, whether or not it is happening and whether or not it is being caused by our carbon dioxide emissions is a question for science. If you want to deny climate change, you need to do so based on evidence, and good luck with that, because the evidence is pretty overwhelming! And by evidence I don’t mean what the talking heads on CNN or NPR or Fox News or some nutty lady on community radio says. Get as close as you can to the source, the people doing the investigating. They are the ones in the trenches, looking at this day in and day out. And I’ll tell you, they are pretty alarmed with what they are learning.

We’ll look more at the climate system and what scientists are finding so alarming in the coming weeks.

 

References:

Andy Borowitz’s great post on Climate change and the winter that wouldn’t quit being so hardcore: http://www.newyorker.com/online/blogs/borowitzreport/2014/01/polar-vortex-causes-hundreds-of-injuries-as-people-making-snide-remarks-about-climate-change-are-pun.html

There is SO MUCH information out there on the web about climate change, but some of the nicest and most concise is from NASA’s Earth Observatory: http://earthobservatory.nasa.gov/Features/GlobalWarming/page1.php

The Wild and the Domestic: Chickens and Broodiness

Note: This program originally aired August 17, 2013.

Last week’s show, was admittedly, very fun, and I hope you enjoyed it (to listen click here). This week however I want to take a few moments and relay some interesting information I discovered, pertaining to chickens and broodiness, and the poultry community in general.

It turns out that if you do any research on the causes of broodiness (the tendency of a hen to want to sit on a nest and incubate eggs, instead of just visiting the nest to lay a daily egg), two distinct conversations emerge. The first includes the backyard chicken community, those raising a small flock of birds for eggs and pleasure. Their information is purely anecdotal and covers a wide range of observations and advice. The other conversation is from the scientific community, particularly the scientific community working for the poultry industry. The thrust of their research is in preventing broodiness, as it interrupts the hens’ laying, and laying eggs is what it is all about (for that sector of the industry). Every day a hen lives but doesn’t lay an egg is a waste of resources in the eyes of industry. These two perspectives make for interesting reading, as you can imagine.

I am curious about what triggers a hen to go broody, and in asking this question we have to keep in mind a few things. First, chickens are birds, and second they are domesticated and selectively bred. In saying that they are birds, we acknowledge that they retain some physiologic and behavioral traits of wild birds. Their domestication has reduced or altered some of those traits. In the wild birds mate and then lay fertilized eggs, usually a set number, a clutch, and then incubate them. This is generally tied to environmental conditions, particularly day length. Chickens are birds, so yes, they lay eggs. They were domesticated approximately 4000 years ago from a south Asian bird called Red Jungle Fowl. These wild ancestors look a lot like chickens, but have a much more typical reproductive pattern, laying fertilized eggs in clutches a few times a year. In the domestication process however, the relatively rare (in the wild) trait of laying unfertilized eggs has been emphasized over and over again, to the point where domestic chickens can lay an egg nearly every day for a year or more, with the rate of egg laying tapering with age. Hens can lay eggs for their entire lives and never even see a rooster.

If you ask an online backyard chicken keeping forum what causes a chicken to go broody, or better yet, how to make your chicken go broody, you will get a plethora of responses which range from dumb luck, to leaving eggs under the hen, to putting dummy eggs or even golf balls under the hen, to day length and season, to breed. The most common theme seems to be the accumulation of eggs in the nest, which appears to trigger something in the wild bird part of the chickens’ wee little brain, something that says “yes, you have your clutch, now sit on it”. If we think about the implications for chicken neurology, that means that the part of the chicken brain that decides to be broody is separate from the part of the chicken brain that is used for mating; interesting, and based on our evidence, totally anecdotal. If you look in the scientific literature for the cause of poultry broodiness a totally different plot develops. It turns out there isn’t much in the literature about the causes of poultry broodiness, only how to prevent it. And that is because most of the research on chickens is done for the benefit of the poultry industry, either by industry scientists or agricultural extension agencies. These studies describe in detail what happens when a chicken goes broody (brain chemistry changes in ways similar to mammals, the pituitary gland triggers the production of the hormone prolactin, which among other things, inhibits gonadotropin stimulated ovulation, i.e. egg laying), but don’t really examine why chickens exhibit this behavior. It is sort of like the question is mute, chickens are birds, that’s why they go broody, what we need to know is how to stop it. And that is what the studies are all about—tests of what they can inject in or feed to chickens to prevent the surge of prolactin that causes the cessation of egg laying, which is the bottom line for the egg industry.

So I never got my question answered. Science has never looked at the question of why a chicken goes broody or how to make a chicken go broody, because industry has no need for that, they have machines that incubate eggs instead. On this I will throw my lot in with the backyard chicken crew, observing, questioning, testing and doing informal science with the best of them. And not knowing the answer doesn’t really bother me.  I actually prefer that some things lay beyond our control, and that mysteries in nature abound. If there were no mysteries, our curiosity would have no food, no medium on which to grow and flourish, and that would be as soul killing as any cement floored mechanized egg producing factory farm. So the next time you crack an egg, pause, and ponder, what you know about that egg, and more importantly, what you don’t know.

References:

Advice from Mother Earth News: http://www.motherearthnews.com/homesteading-and-livestock/encourage-hens-to-hatch-eggs.aspx#axzz2actDPDU

Originally published in Backyard Poultry http://www.themodernhomestead.us/article/broody-hens-1.html

From the USDA (mainly focused on how to prevent broodiness in commercial flocks): http://www.ars.usda.gov/is/ar/archive/nov95/broodiness1195.htm?pf=1

 Way , way , way more than you ever wanted to know about prolactin: http://www.sp.uconn.edu/~ttc02001/MCB3210-5210/RA%20%28V%29/PRLR%20Signal%20Transduction%20Pathways.pdf

The original chickens, Red Jungle Fowl: http://www.gbwf.org/pheasants/junglefowl_red.html

A bit about chicken domestication:
http://www.sciencedaily.com/releases/2008/02/080229102059.htm

The Nature of Science

 Note: This program first aired on January 12, 2012.

What is science? How do we know what we know (or think we know)? Most of us encountered the venerable “Scientific Method” at some point in our schooling, but what does that really mean, and is it how science really works? What are the assumptions we must make about knowledge and how we get it, assumptions that make knowledge actually meaningful. Does science have any limits? I bring these questions up in the context of this program because most of what we talk about here is based in and has been revealed through science.

More than anything else, science is a way of seeing and interacting with and understanding the world. It is a mind set and a way of thinking. It seeks clarity and articulation. Science is simply trying to explain the world around us, using patterns to construct an architechture of explanation, a beautiful lattice of ideas that connect one aspect of the world to the next. The idea that the world is indeed knowable is fundamental to the nature of science. We have to believe that we can learn things about the world to embark on a journey of scientific knowledge. Related to this is the idea that science is limited to knowledge of the natural world, a world we can experience through our senses; I see this, I hear this, I smell this. Ultimately our observations must be testable, quantifiable and repeatable. For example I can simply believe in the tooth fairy, but to support the theory of her existence in the natural world I would need to see her every time I lost a tooth, and other people would as well.

We are all born scientists. You watch the world, you notice something.
“Hmm that was interesting. I wonder if that happened for a reason or was just a coincidence?” That is the essence of science right there, asking questions and trying to separate the patterns from the coincidences. If what we observed is part of a pattern, it means we can make a prediction about what will happen in the future. If the effect we noticed is real, we can predict the effect will happen again if we create the same circumstances. If we keep creating the same circumstances and keep getting the same effect, we can establish knowledge of a relationship between one thing (the effect) and another (the circumstances in which the effect happens). We’ve just learned something about the natural world, or at least, we think we learned something. That’s the thing about science, it can never stop. We have to keep pushing and probing the nature of our question, ultimately trying to prove ourselves wrong. In doing so expand the boundaries and hone the edges.

When we can’t demonstrate that our predictions are wrong, it lends credence to the idea that they may be right; what we observed and our reasons that explain the observation may indeed be correct. But here’s the rub: That’s as close as we get; I might be right, I’m probably right, I’ve looked and looked and there is no evidence that says I am wrong. The closest we get to “knowing” is making accurate predictions. So you must take the headlines about this new scientific finding or that new scientific finding with a kernel of understanding, and rather than feel cynical when months later said headline falls from favor and is quote “proven” wrong, you should embrace the finding as part and parcel of our ongoing and constantly revising attempts to understand the world we live in.

References:

 Great stuff from the Indiana University Evolution and the Nature of Science Institutes http://www.indiana.edu/~ensiweb/home.html

From the American Association for the Advancement of Science: www.project2061.org/publications/sfaa/online/sfaatoc.htm

Of Mice and Oogonial Stem Cells

Note: This program first aired on Deecmber 29, 2012.

I was asked by a listener recently, if female chickens are born with all of the eggs they will lay over the course of their lives, like human females are. This made me wonder if all females have this characteristic, if that is a distinguishing feature of being female—that the cells that become the gametes form in the embryo, and are not replenished as the individual matures. Conventional wisdom states that we females have a set amount of eggs (more than likely more than we will release in the reproductively active period of our lives), we do not make more as we go along. This is in contrast to males, who are able to continually replenish their supply of gametes.

We need to pause for a moment and return to high school biology, and revisit the concepts of meiosis and mitosis. Our cells have two sets of DNA in them, one from our mother and one from our father. That DNA is in the form of chromosomes. Mitosis is simple cell division, we get two cells when we started with one. The chromosomes in the cell all line up, split in half, and each half then replicates itself in the new cell; each new cell ends up with two sets of chromosomes, just like the parent cell had. Meiosis is cell division that results in the formation of gametes. What makes gametes special is that they have only one set of DNA in them, a mash up of DNA from the mother and the father. In meiosis, the chromosome pairs line up, swap DNA and then get separated from each other into two separate cells. Then the chromosomes themselves split in half, and the halves end up in two more cells, yielding a total of four cells from the original one, each with a single set of genetic information. That is what makes gametes gametes, they have only one set of DNA and they need to join with another gamete cell to get a full set of genetic information, enough to make a new individual. The traditional thinking has been that , at least in mammals, meiosis occurs in the ovaries of the embryo. As a female’s reproductive organs are forming, meiosis is going on, and all the eggs the female is going to have are formed then.

Before we get to the chicken issue, I have to break it to you that the conventional wisdom here has been shown to be wrong. As early as 2004, researchers discovered that in mice, the females seemed to be able to maintain a supply of healthy living eggs, even when fed toxins that would kill their follicles. This meant that the mice could generate new eggs, a discovery that flies in the face of the conventional understanding that mammals are born with the only eggs they will ever have. Since then researchers have identified the stem cells in human ovaries, called oogonial stem cells, that do the same thing for us. These oogonial stem cells are able to undergo meiosis at any point and produce new oocytes or eggs. What isn’t clear is if these oogonial stem cells are just a back up system, or if they share responsibility for egg production with the original meiotic cells in the ovary.


So, on to chickens. It turns out this is a very difficult question to answer definitively. Most of the literature refers to the “all the eggs you’ll ever make” phenomena as occurring in either mammals, or “higher animals ” (which by the way are apparently all vertebrates except fish). There is, thus far, no evidence of oogonial stem cells in chickens, but that doesn’t mean they aren’t there, it just means no one has looked, which is a different thing altogether. Likewise, this conventional wisdom principle has likely been laid like a blanket on top of our knowledge of all “higher animals”, meaning, it is unlikely that scientists have studied the embryos of every species close enough to declare that all higher animal females are always born with all their eggs. To be fair, closely related things usually behave in closely related ways, so this blanket technique may not be as imprecise as I am making it sound. We do know that certain worms continually make new oocytes, so it is not unheard of in that natural world, but chickens are closer to the higher animals than to round worms.

The final word? I suspect that chickens, like humans, make most of their eggs during the development of the embryo, and may, like humans, potentially retain the ability to generate new eggs as needed. This question illustrates nicely, the limits of our knowledge, and way we construct what we know, or think we know about the natural world. Thanks Greg, and keep your questions coming.


References:

From Science Daily, a digest of the original study from Massachusetts General Hospital and the University of Edinburgh, demonstrating that female mice can grow new eggs: http://www.sciencedaily.com/releases/2012/07/120726180259.htm

National Geographic’s take on the same study: http://news.nationalgeographic.com/news/2012/02/120229-women-health-ovaries-eggs-reproduction-science/

Need a review of mitosis and meiosis? Check out this nice slide show from the good folks at PBS: http://www.pbs.org/wgbh/nova/miracle/divide.html

A bit here on the traditional take on female oocyte development: http://anthro.palomar.edu/biobasis/bio_2.htm

Whoa. Here’s a scientific article about what can regulate meiosis in chickens!! http://www.biomedcentral.com/1471-213X/8/85

The truth? Its complicated… http://rstb.royalsocietypublishing.org/content/277/955/201.short