Misc

In part 3 of this series I recapped the method derived in part 2 for estimating growth rates (using Howard County’s population in the 21st century as an example) and discussed how to use such estimates to project growth in future years. Now let’s go back to a question I asked at the end of part 2: Can we calculate a more accurate estimate for the growth rate? We can begin exploring this question by going back to my original inaccurate estimate in part 1 and considering where I went wrong. To get that estimate I simply took the final population in 2010, divided it by the initial population in 2000, then divided that by 10 to get an annual growth rate (which I then converted to a percentage value). That initial estimate was too high: When I used that value to estimate the population in 2001, 2002, and so on, it produced a final population estimate for 2010 that was well in excess of the actual 2010 population. ...

In part 2 of this series I discussed a more correct approach to the problem of estimating growth rates, using Howard County’s population in the 21st century as an example. Given the population figures for the 2000 and 2010 censuses, we can estimate an annual growth rate as follows: Divide the final population in 2010 by the initial population in 2000. Take the 10th root of the result from step 1 to find the growth factor. (We use 10 because the period we’re considering is 10 years long.) Subtract 1 from the growth factor to find the growth rate. Multiply the growth rate by 100 to convert it into percentage form. Recall that you can take roots using a scientific calculator app for your smartphone, tablet, or PC, as described in the last post; you can also compute roots in a application like Microsoft Excel or Google Spreadsheets.1 ...

In my last post I introduced the problem of estimating growth rates, using Howard County’s population in the 21st century as an example. I took a simpleminded approach: Take the difference between the county’s population in 2010 and 2000. Divide that difference by the population in 2000 and multiply by 100 to get the percentage growth increase from 2000 to 2010. Divide that percentage by 10 to get an estimate of the population growth per year. As we saw in the last post, the simpleminded approach produces an incorrect answer: the estimated growth rate is too large. In this post I’ll show a more correct way to estimate the growth rate. As before, I’ll avoid mathematical notation and restrict myself to operations you can do on a calculator or in a program like Microsoft Excel or Google Spreadsheets. ...

[I’m interrupting my series of “weekend reading” posts to bring you an actual blog post.] Last week at work one of my tasks was estimating growth rates for a particular quantity (never mind exactly what). I found that doing this was not exactly trivial, as there are multiple ways to calculate growth rates, some of them more mathematically complicated than others. I think I now understand how this all works, and to test my understanding I’m going to try to explain it here. ...

This week my theme is the search for one’s ancestors and the surprising places it can take us: The founders of Anne Arundel and Howard Counties, Maryland (Joshua Dorsey Warfield). Have you ever wondered about the people whose names are reflected in local places (Scaggsville), roads (Snowden River Parkway), and neighborhoods (Shipley’s Grant)? This is one of the (if not the) ur-texts of genealogy in Howard County: “At the beginning of this new century we are going to the garrets, bringing out the portraits of our forefathers, brushing off the dust,—putting them into new frames and handing them down to our children. Search the records for their good deeds.” See also the Howard County Genealogical Society.1 Finding Your Roots with Henry Louis Gates, Jr. (PBS). Genealogy gets the reality show treatment, complete with the requisite dramatic reveals at the conclusion of each episode: “Working closely with leading US genealogists . . . and ancestry experts from around the world, Gates and his production team comb through family stories to discover unknown histories and relatives the guests never knew existed. When paper trails end for each story, the team turns to top geneticists and DNA diagnosticians . . . to analyze each participant’s genetic code, tracing their bloodlines and occasionally debunking their long-held notions and beliefs.” You can view all the episodes online; I watched the one with Cory Booker and John Lewis, which has an especially moving narrative involving Lewis’s ancestors. “DNA Testing for Genealogy—Getting Started, Part One” (CeCe Moore). If your relative who keeps the family history starts talking about SNPs, haplotypes, and mitochondrial DNA, now you’ll know why: “Interest in DNA testing for genealogy has reached an all-time high thanks to its increasing sophistication and the resulting visibility in the media. . . . As a result, many family history enthusiasts have expressed their desire to venture into the fascinating world of genetic genealogy, but don’t know where to start. If you are one of these people, then I am writing this for you.”2 ”About the Genographic Project” (National Geographic Society). The National Geographic Society continues its tradition of making the exotic familiar: “We have developed a cutting-edge new test kit, called Geno 2.0, that enables members of the public to participate in the Genographic Project while learning fascinating insights about their own ancestry. . . . Included in the markers we will test for is a subset that scientists have recently determined to be from our hominin cousins, Neanderthals and the newly discovered Denisovans. . . . With Geno 2.0, you will learn if you have any Neanderthal or Denisovan DNA in your genome.” “Neandertals Live!” (John Hawks). Hawks is an anthropologist at the University of Wisconsin-Madison and a prolific blogger. Here he reacts to the announcement of the sequencing of the Neandertal genome and the evidence that some (not all) humans have Neandertal ancestry: “These scientists have given an immense gift to humanity. I’ve been comparing it to the pictures of Earth that came back from Apollo 8. The Neandertal genome gives us a picture of ourselves, from the outside looking in. We can see, and now learn about, the essential genetic changes that make us human—the things that made our emergence as a global species possible.” Hawks also has some things to say about the Denisovans.3 “‘Bigfoot’ DNA Sequenced In Upcoming Genetics Study” (Dr. Melba Ketchum and associates). Perennially frustrated Sasquatch hunters want to join the genome sequencing archaic human interbreeding fun: “The genome sequencing shows that Sasquatch [mitochondrial DNA] is identical to modern Homo sapiens, but Sasquatch [nuclear DNA] is a novel, unknown hominin related to Homo sapiens and other primate species. Our data indicate that the North American Sasquatch is a hybrid species, the result of males of an unknown hominin species crossing with female Homo sapiens.” However they didn’t release the actual genome data, so for now this remains just a tease, the scientific equivalent of Finding Bigfoot.4 The Warfield book is in the public domain, so I’ve pointed to the free downloadable copy in the Internet Archive. You can also find versions in various formats at Amazon or elsewhere; some of these may feature cleaner conversions of the text. ↩︎ ...