Jeff Danner: Hometown Hero

Jeff Danner is Tuesday’s Hometown Hero.

For the past five years, Jeff has written the Common Science column on  Danner uses the column to explain the wonderful and complicated world of science in a way we all can understand.

Overall, Jeff Danner has written over 200 columns for Chapelboro.  To celebrate, we took a look back five of his most popular Common Science columns.

Happy Five Years at Chapelboro, Jeff Danner!

Read more Common Science.

You can nominate your own Hometown Hero.  WCHL has honored local members of our community everyday since 2002.

Last Year In (Common) Science

Every week on, our resident science expert Jeff Danner writes a column called “Common Science.” This year he’s tackled everything from solar bees to microbiomes to cold fusion…and that’s just scratching the surface. (Speaking of which, he also wrote about fracking.)

You can read Jeff’s entire archive here – not just all of 2015, but nearly five years’ worth of Common Science columns.

Last week on WCHL, Jeff Danner and Aaron Keck looked back on 2015 in Common Science. Listen to their conversation.

Common Science Comprehensive Index

April 2015 will be the fourth anniversary for Common Science®. In each of the past three Decembers I have published a hyper-linked index for the columns from that year. This year I decided to do something different. Below is an index with links to all 185 columns I have published.

I have some new ideas for Common Science® for 2015. I’ve been writing for 3.5 years, doing the radio spot (Mondays at 4:32 on 1360 AM/97.9 FM WCHL, Chapel Hill, NC), and have been running a Twitter Feed, @commonscience, for about a year. Lately, I have been evaluating where to go next. I’ve written an outline for a book and also started to develop some materials to teach a class or workshop on some of the topics I have covered. My friend Robert has suggested that I start up a companion website for my columns on I’m also developing a logo.

This comprehensive index has helped me to sort through my thoughts on possible new directions. For you, I hope it can serve as a bit of a reference e-book of easy-to-understand science explanations accompanied by my (hopefully) interesting, insights and commentaries.

I particularly enjoy receiving correspondence from readers at With rare exceptions, I respond to all of them. So if you have a comment or question on something I have written about or want to suggest a topic for a future column, shoot me a note.

Common Science Comprehensive Index


1              April 25, 2011                     An Introduction to Your Host

2              April 25, 2011                     Photosynthesis Part I: Oxygen Gets All the Press

3              April 27, 2011                     Nothing Matters More than Oil, Nothing

4              May 5, 2011                        Local Deal: 60% Off Hot Water

5              May 10, 2011                      Dating an Engineer

6              May 16, 2011                      Photosynthesis Part II: Glucose Needs a New Agent

7              May 20, 2011                      Shelter from the Storm

8              June 1, 2011                       Petroleum: 300 Million Years of Sunlight

9              June 5, 2011                       Is Your Cell Phone Trying to Kill You?

10           June 11, 2011                     Farewell to Brood XIX

11           June 18, 2011                     Peak Oil in Five Paragraphs or Less

12           June 27, 2011                     Lessons for Chapelboro from George Washington

13           July 4, 2011                         Gas Prices and the Dow Jones

14           July 10, 2011                       A Science Question for Michele Bachman

15           July 17, 2011                       Fun with Fritz and Carl

16           July 29, 2011                       Welcome to the Greenhouse

17           August 8, 2011                   Electricity Production 101

18           August 14, 2011                To Frack or not to Frack

19           August 22, 2011                The World’s Greatest Cheat Sheet

20           August 24, 2011                Earthquake!

21           September 5, 2011            It’s a Theory that’s Out There

22           September 11, 2011         Everything Comes from Oil, Everything

23           September 19, 2011         Flu Season Primer Part I: The Virus

24           September 25, 2011         Flu Season Primer Part II: The Immune System

25           October 2, 2011                Flu Season Primer Part III: The Flu

26           October 9, 2011                The Flu: Epilogue

27           October 16, 2011              Entropy and the Local Economy

28           October 20, 2011              The Saudi Arabia of Denial

29           October 30, 2011              iPads, Priuses, and Neodymium

30           November 7, 2011           It’s Getting Crowded in Here

31           November 13, 2011          Your Mother the Plant

32           November 21, 2011         Carbon Monoxide – The Silent Killer

33           November 28, 2011         Advice to My Nephew on Whether to Study Science or Engineering

34           December 5, 2011            Biofuels Part I: Biodiesel Basics

35           December 12, 2011          Biofuels Part II: The Secret Life of Vegetable Oil

36           December 18, 2011          Biofuels Part III: Ethanol, It’s not Just for Breakfast Anymore

37           December 27, 2011          “A Year from Now You Will Wish You Had Started Today”

38           January 9, 2012                 Chapelboro 2050 Part I: Life on Two Wheels

39           January 16, 2012               Chapelboro 2050 Part II: A Farewell to Lawns

40           January 22, 2012               Yes, We Have no Bananas

41           January 29, 2012               Chapelboro 2050 Part III: Get into the Zone

42           February 6, 2012               Chapelboro 2050 Part IV: The Good Dirt

43           February 12, 2012            2012 The Year Without Winter

44           February 20, 2012            Keystone Controversy

45           February 27, 2012            What a Fracking Mess

46           March 5, 2012                    Follow the Bouncing Rubber Ball

47           March 12, 2012                  Water Part I: Is God a Mathematician?

48           March 19, 2012                  Lessons from the Explosion in the iPad Factory in China

49           March 26, 2012                  Water Part II: Water, Water Everywhere, Nor Any Drop to Drink

50           April 1, 2012                        Water Part III: Get the Salt Out

51           April 9, 2012                        Water Part IV: When the Well Runs Dry

52           April 23, 2012                     Another Piece of the Fracking Puzzle

53           April 30, 2012                     Water Part V: When Oil and Water Mix

54           May 7, 2012                        Getting Ready for Summer with SPF

55           May 14, 2012                      Yes This Really is a Column about Phosphorous

56           May 21, 2012                      Fracking, What NPR Left Out

57           May 28, 2012                      Gravity, Still a Mystery

58           June 4, 2012                       The Transit of Venus

59           June 11, 2012                     Bronze Age Part I: Intelligence versus Accumulated Knowledge

60           June 18, 2012                     Bronze Age Part II: The Case of the Missing Copper

61           June 24, 2012                     High Fructose Corn Syrup, One Lump or Two?

62           July 2, 2012                         Don’t Know Much Biology

63           July 9, 2012                         The God Particle

64           July 16, 2012                       Don’t Sweat It

65           July 22, 2012                       Welcome to the Greenhouse: Reprise

66           July 29, 2012                       To Frack or not to Frack: Reprise

67           August 6, 2012                   When the Lights Go Out

68           August 12, 2012                Don’t Let the Bed Bugs Bite

69           August 20, 2012                Marriage Advice from Common Science

70           August 26, 2012                The Science Behind WCHL, Your News, Talk, and FM Station

71           September 3, 2012          West Nile Virus

72           September 10, 2012        If We Mine it or Drill It, We’re Going to Burn it

73           September 17, 2012        Nuclear Power Part I: The Science

74           September 24, 2012        Nuclear Power Part II: Waste, No Solution So Far

75           September 30, 2012        Nuclear Power Part III: Safety and Conclusion

76           October 8, 2012                Why This is an Important Year to Get Your Flu Shot

77           October 15, 2012              Deep Sea Vents, The Key to the Biggest Question in the Universe?

78           October 22, 2012              Political Non-Science Part I

79           October 28, 2012              Political Non-Science Part II: Calling Dr. Holdren

80           November 4, 2012           Nanotechnology

81           November 6, 2012           Why Ohio is not Close

82           November 12, 2012         Risky Business

83           November 19, 2012         Methane Hydrate Part I: The Science

84           November 26, 2012         Methane Hydrate Part II: All You Really Need to Know About Global Warming

85           November 30, 2012         Common Science Flash Post: Flu Season Update

86           December 3, 2012            The Greatest Invention of the 21st Century

87           December 10, 2012         An Ode to President Carter

88           December 16, 2012         The Lesson of Nylons

89           December 31, 2012          Common Science: The Year in Review

90           January 7, 2013                 A Follow-Up Question for Mr. Skvarla

91           January 14, 2013               Hemp, George Washington Grew It

92           January 20, 2013               In Which I Reveal Myself to be a Luddite, At Least Partly

93           January 27, 2013               Perils of a Hyper Hygienic Existence

94           February 4, 2013               Bananas Will Never Grow in Barrow

95           February 10, 2013            Dear God What is that Smell?

96           February 18, 2013            Food Part I: Three Book Recommendations

97           February 24, 2013            Food Part II: The Science of the Stomach

98           March 4, 2013                    Food Part IIIA: Wonder Bread is not Wonderful

99           March 11, 2013                  Food Part IIIB: An Apple a Day Really Did Used to Keep the Doctor Away

100         March 18, 2013                  Common Science Column 100

101         March 24, 2013                  Food Part IV: The Chicken and the Egg

102         March 31, 2013                  Food Part V: Conclusion and Some Politics

103         April 15, 2013                     National Helium Shortage

104         April 21, 2013                     Want to Grow the Local Economy? Hire More Engineers

105         April 29, 2013                     Advice for Opponents to the Keystone XL Pipeline

106         May 6, 2013                        Depleted Uranium

107         May 12, 2013                      Cougars in Chapel Hill in 2035?

108         May 19, 2013                      Ten Things You Should Know about CO2 Topping 400 PPM

109         May 26, 2013                      Mentors

110         June 3, 2013                       Hurricanes Part I: Hurricane Barry

111         June 10, 2013                     Hurricanes Part II: Storm Surge

112         June 16, 2013                     Hurricanes Part III: Frequency and Global Warming

113         June 23, 2013                     Voyager I: Off to Interstellar Space

114         July 1, 2013                         Empire of the Ants

115         July 8, 2013                         No Where Else for the Rain to Go

116         July 21, 2013                       The Power of Backpacking

117         July 29, 2013                       Monkey Pox . . . Seriously?

118         August 5, 2013                   Something is Rotten in the Province of Alberta

119         August 11, 2013                The Caterpillar Effect

120         August 19, 2013                Could Caesar Eat Peanuts?

121         August 25, 2013                The Rise and Fall of U.S. Infrastructure Part I: The Rise

122         September 1, 2013           The Rise and Fall of U.S. Infrastructure Part II: The Fall

123         September 8, 2013           The Rise and Fall of U.S. Infrastructure Part III: Conclusion

124         September 16, 2013         The Butterfly Effect

125         September 23, 2013         A World without Fossil Fuels

126         September 29, 2013         Bacteria and Obesity, A Surprising Link

127         October 6, 2013                Your Sister the Mushroom

128         October 13, 2013              Fungi of the Future

129         October 20, 2013              How Engineers Spend Their Spare Time

130         October 27, 2013              The Uncommon Core of the New Math

131         November 3, 2013           The Physics of Your Fireplace

132         November 10, 2013         Sudden Cardiac Arrest Part I: The Heart

133         November 17, 2013         Sudden Cardiac Arrest Part II: Heart Attack or Cardiac Arrest

134         November 24, 2013         Sudden Cardiac Arrest Part III: First Aid

135         December 1, 2013            It’s the Extraction, Not the Emissions, That Matter

136         December 8, 2013            Sudden Cardiac Arrest Part IV: The Frozen Man

137         December 15, 2013         Smog, The Desolation of Shanghai

138         December 22, 2013         Common Science 2013 Index

139         January 5, 2014                 2014 Predictions Part I: The Positive

140         January 12, 2014               2014 Predictions Part II: The Negative

141         January 19, 2014               We Can Afford More Math Textbooks

142         January 26, 2014               West Virginia Chemical Spill

143         February 2, 2014               My First PC Weighed 25 Pounds

144         February 10, 2014             Keystone Pipeline Update

145         February 16, 2014             A Tale of Two Spills

146         February 23, 2014             The Case of the Missing Propane

147         March 3, 2014                    Checking In on Peak Oil

148         March 16, 2014                  China, The Canary in the Coal Mine

149         March 23, 2014                  3D Printing Part I: The Technology

150         March 31, 2014                  The Birthday Problem

151         April 6, 2014                        3D Printing Part II: The Future

152         April 13, 2014                     3D Printing Part III: A UNC Connection

153         April 20, 2014                     The Vanishing of the Bees Part I: Psychology

154         April 27, 2014                     The Vanishing of the Bees Part II: Local Efforts

155         May 4, 2014                        My Conflicting Thoughts on Beekeeping

156         May 12, 2014                      Meanwhile, In the War on Science

157         May 18, 2014                      Renewable Energy is Sort of like the Internet

158         May 26, 2014                      Fracking Gag Rule Part I: Trade Secret?

159         June 1, 2014                       Fracking Gag Rule Part II: The Real Reasons

160         June 8, 2014                       Fracking Gag Rule Part III: Wastewater

161         June 29, 2014                     Brazil and BBQ

162         July 6, 2014                         Hello, Arthur

163         July 13, 2014                       Chikungunya is Coming: Part I

164         July 20, 2014                       Chikungunya is Coming: Part II

165         July 27, 2014                       Soil Part I: Seaweed Fertilizer

166         August 3, 2014                   Meanwhile in the Arctic

167         August 10, 2014                Soil Part II: An Optimistic Global Warming Column

168         August 17, 2014                Methane in the Water Part I: Toxicity

169         August 24, 2014                Methane in the Water Part II: Fires and Explosions

170         August 31, 2014                Why Solar Roads Are a Bad Idea

171         September 7, 2014           How to Teach an Engineer to Play Guitar

172         September 14, 2014         All About Electricity

173         September 21, 2014        Chikungunya Part III: The Epidemic Continues

174         September 28, 2014        Of Minerals and Men

175         October 5, 2014                Mercury Rising

176         October 12, 2014              The Case of the Disappearing Lakes

177         October 20, 2014              How Chemical Engineering is Like Calculus

178         October 26, 2014              Common Science Grab Bag

179         November 2, 2014           Spinal Cord Miracle?

180         November 9, 2014           Is the Toilet the Greatest Public Health Invention Ever?

181         November 16, 2014         Why are the Norwegians Burning Trash?

182         November 23, 2014         An Engineer on a Diet: Part I

183         November 30, 2014         An Engineer on a Diet: Part II

184         December 7, 2014            Fracking: A Raleigh-Riyadh Connection

185         December 14, 2014         Results of My 2014 Predictions

Common Science 2013 Index

Below is my third annual index for Common Science on  I’d like to thank my readers for their support and for all of the interesting questions I have received from you at  Just follow the hyperlinks below to read any of this year’s stories. And if there is a topic you would like me to cover in 2014, send me an email.

Happy Holidays from Common Science!

1.     A Follow-Up Question for Mr. Skvarla                                                    1/6/13

An evaluation of the North Carolina Secretary of the Department of Environmental and Natural Resources’ view that global warming is still an open question.

2.     Hemp, George Washington Grew It                                                         1/13/13

A review of the remarkable properties of the hemp plant and the history of why we stopped growing it.

3.     In Which I Reveal Myself to Be a Luddite, at Least Partly              1/20/13

A personal confession regarding my affection for hand tools.

4.     Perils of a Hyper Hygienic Existence                                                        1/27/13

Some of the health challenges presented by trying to keep all bacteria out of our lives.

5.     Bananas Will Never Grow in Barrow                                                        2/3/13

An explanation of why plants will not be able to migrate fast enough to keep pace with global warming and the implications of this for the world’s food supply.

6.     Dear God What is That Smell?                                                                     2/10/13

The science behind women’s superior sense of smell.

7.     Food Part I: Three Book Recommendations                                          2/17/13

Book reviews on three recent books about our food supply.

8.     Food Part II: The Science of the Stomach                                                           2/24/13

How the digestive system deconstructs our food and conveys needed nutrients to the rest of our body.

9.     Food Part IIIA: Wonder Bread is not Wonderful                                 3/3/13

A review of the aspects of the U.S. industrial food system which are making our diets less and less healthy.

10. Food Part IIIB: An Apple a Day Really Did Used to Keep the Doctor Away        3/10/13

The conclusion of Part III.

11. Common Science Column 100                                                                          3/17/13

A thank you column to my readers to mark my 100th column.

12. Food Part IV: The Chicken and the Egg                                                        3/24/13

The shortcomings of factory chicken farms in providing us with healthy and nutritious food.

13. Food Part V: Conclusion and  Some Politics                                               3/31/13

The conclusion of my series on food with advice for the individual, our local region, and our nation on how to improve our food system and live healthier lives.

14. National Helium Shortage                                                                                  4/15/13

Reasons why elements do not obey the law of supply and demand, and the politics behind our helium shortage.

15. Want to Grow the Local Economy? Hire More Engineers.                  4/22/13

An argument that the foundation of value creation is the transformation of raw materials into finished goods, and that more engineers are needed to boost this process.

16. Advice for Opponents of the Keystone Pipeline                                       4/29/13

An argument that the focus on pollution of water supplies by pipeline leaks is the wrong focus for those trying to stop the pipeline project.

17. Depleted Uranium                                                                                                 5/6/13

An explanation of what depleted uranium is, what it is used for, the health problems it creates, and the challenges of cleaning it up in Iraq.

18.Cougars in Chapel Hill in 2035                                                                        5/13/13

Using the data for the expansion of the range of the cougar from the Rockies to the Mississippi in conjunction with Fick’s Law of Diffusion, I predict that Cougars will return to Chapel Hill, NC in 2035.

19. Ten Things You Should Know About CO2 Topping 400 PPM         5/20/13

An explanation of the significance of the concentration of carbon dioxide in the atmosphere reaching the 400 ppm milestone and the implications for the future.

20. Mentors                                                                                                                    5/27/13

The story of three important mentors in my life and the lessons they gave me.

21. Hurricanes Part I: Hurricane Barry                                                            6/3/13

The science behind hurricanes.

22. Hurricanes Part II: Storm Surge                                                                  6/10/13

An explanation of why most of the damage and loss of life from Hurricanes is the result of storm surge.

23. Hurricanes Part III: Frequency and Global Warming                        6/17/13

An explanation of why warmer oceans may result in stronger hurricanes but not more frequent storms.

24. Voyager I: Off to Interstellar Space                                                             6/23/13

After decades of travel, the first man-made object will be leaving our solar system and sending back data from interstellar space.

25. Empire of the Ants                                                                                              7/1/13

The invasion of the Southeastern United States by the Tawny Crazy Ant.

26. No Where Else for the Rain to Go                                                                 7/8/13

An explanation of how outdated storm water systems contributed to the Great Chapel Hill Flood of 2013.

27. The Power of Backpacking                                                                               7/15/13

After returning from a recent hike on the Appalachian Trail, I calculate the power consumption required to lug a 30 pound backpack up hills over uneven ground.

28.Monkey Pox . . . Seriously?                                                                               7/22/13

Now that we have stopped giving the smallpox vaccine, monkey pox is on the rise.

29.Something is Rotten in the Province of Alberta                                       8/5/13

The details behind a “spill” from a tar sands well in Alberta and an explanation of why this type of event will continue to occur.

30.The Caterpillar Effect                                                                                          8/12/13

We all plant flowers to attract butterflies, but what we are not doing is giving their caterpillars anything to eat.

31. Could Caesar Eat Peanuts                                                                                 8/19/13

The surprising correlation between Caesarian birth and food allergies.

32. The Rise and Fall of U.S. Infrastructure Part I: The Rise                 8/25/13

The history of the great investments in U.S. infrastructure from the 1800s through the 1970s.

33. The Rise and Fall of U.S. Infrastructure Part II: The Fall                 9/1/13

The rapid deterioration of U.S. infrastructure which occurred since 1980, after investment as a function of gross domestic product significantly declined.

34.The Rise and Fall of U.S. Infrastructure Part III: Conclusion          9/8/13

A plan for building the infrastructure we need to succeed in the 21st Century.

35. The Butterfly Effect                                                                                               9/15/13

An explanation of the difference between the Butterfly Effect and Chaos Theory.

36.A World Without Fossil Fuels                                                                           9/22/13

My vision of the state of the world today if the earth did not have fossil fuels.

37.Bacteria and Obesity, A Surprising Link                                                      9/29/13

Use of antibiotics in young mammals limits the diversity of gastrointestinal tract bacteria for life, a key factor in the obesity epidemic.

38.Your Sister the Mushroom                                                                                10/6/13

An exploration of the commonality between humans and mushrooms due to their relationship on the tree of evolution.

39.Fungi of the Future                                                                                                10/13/13

Some predictions on the key role that fungi will play in our lives during the 21st century.

40.How Engineers Spend Their Spare Time                                                   10/20/13

My project to install a solar water heating system in my green house to grow tomatoes all year.

41. The Uncommon Core of the New Math                                                       10/27/13

My critique of the new Common Core math curriculum.

42.The Physics of Your Fireplace                                                                          11/3/13

The surprising scientific sophistication of the gas fireplace.

43.Sudden Cardiac Arrest Part I: The Heart                                                    11/10/13

The beginning of a series on the science of sudden cardiac arrest and the story of my father’s remarkable survival of one.

44.Sudden Cardiac Arrest Part III: Heart Attack or Cardiac Arrest      11/17/13

The differences between a heart attack and a cardiac arrest and their symptoms.

45.Sudden Cardiac Arrest Part IV: First Aid                                                     11/24/13

First aid for sudden cardiac arrest.

46.It’s the Extraction, Not the Emissions, That Matters                             12/1/13

Stories about carbon dioxide emissions from individual countries are inherently misleading.  What truly matters in terms of global warming is global extraction of below-ground carbon atoms.

47.Sudden Cardiac Arrest Part IV: The Frozen Man                                  12/8/13

Conclusion of the Sudden Cardiac Arrest series, including the story of how and why therapeutic hypothermia saved my father’s life.

48.Smog, The Desolation of Shanghai                                                             12/15/13

The science behind the devastating smog in Shanghai, China.

It’s The Extraction, Not The Emissions, That Matters

Since personal obligations have kept me busy this week over Thanksgiving, I will not be publishing the conclusion of the “Sudden Cardiac Arrest” series until December 8th. This week, I am reprising a column from September, 2012, with this new introduction, which I hope will help to shed some light on two recent, but seemingly contradictory news stories. In 2013, carbon dioxide emissions in the United States were down by 3.7% compared to 2012. In stark contrast, gloggbal emissions, at a staggering 10 billion tons, were 2.1% higher than in 2012.

Coal_Burning_Power_Plant_Smoke_StacksAs I explained in “If We Mine it or Drill it, We’re Going to Burn It,” news stories which focus on carbon emissions are inherently misleading. Since the air in the atmosphere is all mixed together, it does not matter from which country the emissions originate. The parameter that truly matters is the rate at which we are extracting carbon, in the form of coal, oil, and natural gas, from below the ground.

The widespread utilization of hydraulic fracturing (fracking) combined with horizontal drilling in the U.S. has resulted in a significant increase in extraction of natural gas. Natural gas is difficult and expensive to export, so nearly all of this increased supply is being burned in domestic power plants to make electricity. As more electricity in the U.S. is being generated from natural gas, the amount produced by burning coal is decreasing. Generating an equivalent amount of electricity from natural gas rather than coal releases less carbon dioxide. Therefore, the shift towards natural gas for electricity production in the U.S. is the primary reason that carbon dioxide emissions from the U.S. have been reduced. As nice as this may sound, it doesn’t really matter.

To understand why it doesn’t matter, one need look no further than Appalachia, the heart of the U.S. coal mining industry, rumors of whose death have been greatly exaggerated. Despite the loss of a portion of the electricity market, U.S. coal extraction is at an all-time high. Since coal is easy to transport, it is being shipped all over the world, particularly China and India, to generate electricity there.

The end result of the natural gas “boom” from fracking and the increase in coal exports is an increase in the extraction of underground carbon from the U.S. This is the story that matters about the U.S. contribution to carbon dioxide emissions and global warming. We are making it worse, not better.

For more detail and the underlying science, follow the link above to my previous column. If you have a comment or question use the interface below or send me an email to

Could Caesar Eat Peanuts?

I recently had the chance to read through my stack of the last several months of Scientific American® magazine. My curiosity was piqued a story in one of the issues about a study conducted by the Henry Ford Hospital in Detroit. The study reported that babies who had been born via Caesarian section (C-section) were five times more likely to develop food allergies than those born vaginally. Like many parents I know, I have a strong impression that childhood food allergies are far more prevalent now than in the 1970s when I grew up. I have no childhood memories of peanut-free classrooms or EpiPens.

A search of the CDC and NIH websites provided the data for the graph below.

casarian data

C-section rates have been steadily rising in the United States, from around 5% of births in 1970 to nearly 33% today. The data for childhood peanut and overall food allergies show that not only are childhood food allergies on the rise, but the rate of rise is nearly identical to the rate of increase of C-sections.

We’ll get back to the correlation been allergies and C-sections in a moment, but first permit me a brief aside to do a little math. I read several news reports on the Henry Ford Hospital study which all included the “five times more likely” statement, but omitted any absolute numbers. This is a key gap. For example, if C-sections increased the chance of developing a food allergy from 0.01% to 0.05%, it would probably not be significant enough to factor childbirth decisions.

However, using the data from the graph above and little algebra, it is not difficult to quantify the risks. If the 33% of children born via C-section are five times more likely to develop food allergies, and the total rate of allergies for all children is 5.1%, then the chance that a child born by C-section will develop a food allergy is 11.0% versus just 2.2% for a child born vaginally. This is a noteworthy difference and likely worthy of some consideration by expectant parents.

Getting back to the graph, we can see that childhood food allergies and rates of Caesarian births are closely correlated, but correlation does not necessarily demonstrate causation. The study at the Henry Ford Hospital addressed this issue and developed a convincing case for causation. While in-utero, the gastrointestinal (GI) tract of a child is bacteria free. Beneficial bacteria in your GI tract are essential both to digest food and to ward of disease. Therefore, newborn babies need to rapidly develop a large and diverse population GI tract bacteria.

During a vaginal birth, the baby’s GI tract becomes populated with the mother’s bacteria from the ingestion of fluids through the mouth. This “inoculation” of bacteria from the mother gives the child a tremendous head start towards developing a healthy digestive system. Babies born by C-section only start to populate their GI tract with bacteria from breast milk and/or from sticking their fingers in their mouths. This less efficient approach to establishing a healthy bacteria population appears to dramatically increase the incidence of food allergies. Food allergies may lack a scary-sounding name, but they are by no means a trivial circumstance. Sufferers can experience reduced quality of life, severe reactions, and, in extreme cases, death.

The parallels between this column and the issues I discussed in my recent column entitled “The Perils of a Hyper Hygienic Existence” are striking. Through the use of antibiotics some people have the population of healthy bacteria in their GI tract dramatically reduced in a sustained manner. This circumstance can bring about debilitating diarrhea and a variety of other serious GI tract problems. Recent studies have shown that these patients can experience remarkable improvement by introducing the bacterial flora from a healthy donor by a process rather unfortunately named fecal transplant.

When considering the correlation between Caesarian birth rates and food allergies I thought a similar solution might be appropriate. When Caesarian births are performed, I thought that a methodology might be considered which would introduce the mother’s bacterial flora to the child’s GI tract to help fend off food allergies.  I found a recent study conducted in Venezuela which did just that. They gave the child the bacteria she needed with a simple mouth swab after the C-section. This simple procedure could dramatically reduce the incidence of food allergies in C-section babies.

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Cougars in Chapel Hill in 2035?

You may recall some excitement in Chapel Hill in December of 2008 when there was a reported cougar sighting near the UNC golf course.  Like many cougar sightings in North Carolina, this one was not confirmed by state wildlife officials.  But cougars are on the move eastward from the Rockies and are likely to return to the area some day.  The question is when?  Common Science is here to try to answer that question.

The discussion of cougars gets complicated by the many names given to the species including puma, mountain lion, and catamount.  They are all the same.  Prior to European colonization, cougars ranged through most of the United States and Canada, feeding primarily on deer, elk, and moose.  Cougars, males in particular, are solitary, territorial, and nocturnal.  Their maximum population densities average only four cougars for every 40 square miles, or 0.1 per square mile, a number to which we will refer back later.  Therefore, even when cougars are at their normal population densities, sightings are usually rare.

When U.S. and Canadian settlers pushed westward, they considered the cougar to be a menace and a nuisance and killed them indiscriminately.  Additionally, even though the losses of livestock were statistically low, farmers and ranchers successfully lobbied their respective state governments to pay bounties for dead cougars.  By the 1950s, with the exception of a an isolated population in the Florida Everglades, all cougars east of the Mississippi river had been eliminated and the population between the Mississippi and the Rocky Mountains was nearly wiped out as well.  By the 1960s and 1970s, most states repealed the bounties and imposed regulations against indiscriminate killing of cougars, allowing the populations to begin a slow rebound.  At present, it is estimated that the cougar population in the U.S. is somewhere between 30,000 and 50,000.

The vanguard of a cougar migration consists of juvenile males who need to find available territories to avoid conflicts with older males.  Occasionally a lone male will travel hundreds of miles out of range, which accounts for the infrequent but intriguing reports of cougars along the eastern seaboard, including a recent confirmed sighting in Connecticut.  However, the re-establishment of a stable population in a new area must await the arrival of both genders.  The eastward migration of the cougar is being tracked via confirmed sightings in midwest states, including Oklahoma, Missouri, Illinois, and Arkansas.  Cougar sightings in these states grew from just two in 1990 to 34 in 2008, suggesting a noteworthy increase in population density during this time interval.

This brings me to the reason I find the phenomena of animal migrations to be interesting, and which will usher in the section of this column which is almost certain to differentiate it from any other column you encounter covering the return of the cougar to the eastern United States.   The movement of animal populations can be modeled with diffusion equations, a tool often used by engineers like me.    Diffusion equations are used to determine the rate of movement of materials from an area of high concentration to one of low concentration.  If you’d like to run your own diffusion experiment, put a drop of food dye into a glass of water and watch.  Initially, the area where the drop landed will have high concentration of dye.  With time, molecules of the dye will migrate away from the area of high concentration to zones of water in the glass which have low or no concentration of dye.

The dynamics of this simple kitchen experiment have a lengthy and elegant mathematical explanation which culminates in Fick’s Law of Diffusion. I’m tempted to include a thorough explanation of the underlying mathematics of Fick’s Law, but I’m not so sure you’d be tempted to read it.  What I would like you to consider however, is that the migration of the cougar and the diffusion of the food dye are quite similar.  In the case of the cougars, the area near the Rocky Mountains which contains 0.1 cougars per square mile is like the drop of food dye, and the area bereft of cougars east of the Rockies is like the rest of the water in the glass.  Therefore, we can use Fick’s Law to try to predict when the cougar will return to the southern part of heaven.

If you look at the map below, the western most dashed line runs approximately along the north-south axis of the Rocky Mountains.   About 500 miles to the east, shown by the vertical dashed line called D1  (distance 1), the cougar population density was such that there were just 2 sightings in 1990.  We don’t know the exact population density of cougars along D1 in 1990, but we know it was low.  In my calculations, I assigned it a value of 0.002 cougars per square mile.  I can’t know if this is correct, but as long as I am consistent with the assumption that a population density of 0.002 cougars per square mile will result in 2 sightings per year, the subsequent predictions will still work.  (I need you to trust me on that one.)  The line D2 on the map indicates the location of Chapel Hill, which is approximately 1400 miles east of the Rockies.

Cougar Map

Now that I have the population density of cougars for two locations in 1990, the Rockies and the line D1, I can model the population density of cougars as a function of distance using Fick’s Law.  This is shown by the blue line on the graph below.  By 2008, the number of sightings in the D1 area rose to 34 per year.  Since sightings increased by a factor of 17, from 2 to 34, it is reasonable to assume that the population density increased by a factor of 17 as well.  Using this assumption, the population density as a function of distance for 2008 is shown with the purple line.  The curve for 2008 suggests that by this time cougars should have begun recapturing western Tennessee as part of their range.  News reports conflict as usual, but there is strong anecdotal evidence that they did return to the Volunteer State around that time.

Cougar GraphUsing this model, I can calculate how long it should take for the population density in Chapel Hill to reach 0.002 cougars per square mile, the level at which we could expected to begin to see confirmed sightings from a resident population consisting of both males and females.  This is shown on the graph with the green line, suggesting that in addition to jaguars, tigers, and wildcats (our high school mascots in case you missed the reference), Chapel Hill will have cougars in 2035.  If we ever need to build a fourth High School, then the choice for a mascot is obvious.

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