{"id":5933,"date":"2016-04-26T04:09:24","date_gmt":"2016-04-26T03:09:24","guid":{"rendered":"http:\/\/emilkirkegaard.dk\/en\/?p=5933"},"modified":"2016-04-26T04:12:03","modified_gmt":"2016-04-26T03:12:03","slug":"change-in-egyptian-skull-sizes-4000-to-150","status":"publish","type":"post","link":"https:\/\/emilkirkegaard.dk\/en\/2016\/04\/change-in-egyptian-skull-sizes-4000-to-150\/","title":{"rendered":"Change in Egyptian skull sizes: -4000 to 150"},"content":{"rendered":"<p>I often read statistics textbooks. In textbooks, they often use example datasets, some of which are interesting in themselves (e.g. <a href=\"http:\/\/emilkirkegaard.dk\/en\/?p=5251\">the Boston dataset<\/a>). In this case, I am reading <a href=\"https:\/\/www.goodreads.com\/book\/show\/11953316-an-introduction-to-applied-multivariate-analysis-with-r\"><em>An Introduction to Applied Multivariate Analysis with R<\/em><\/a>. It features a dataset of Egyptian skulls spanning about 4000 years. Given the scholarly interest in dysgenics and <a href=\"http:\/\/www.sciencedirect.com\/science\/article\/pii\/S1041608015300078\">human brain size evolution<\/a>, it seems fitting to analyze this dataset for any historical trends.<\/p>\n<p>The dataset reportedly comes from:<\/p>\n<ul>\n<li>Thompson, A. and Randall-Maciver, R. (1905) Ancient races of the Thebaid, Oxford University Press.<\/li>\n<\/ul>\n<p>I could not find a copy (checked Gutenberg and Libgen) of this book tho it should be free of copyright by now (<a href=\"https:\/\/www.youtube.com\/watch?v=tk862BbjWx4\">!<\/a>). There is a review of it <a href=\"http:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC1287447\/\">here<\/a>.<\/p>\n<p>There are 30 skulls for each time period, 5 periods and 4 measurements.<\/p>\n<p><a href=\"http:\/\/emilkirkegaard.dk\/en\/wp-content\/uploads\/skulls.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-5935\" src=\"http:\/\/emilkirkegaard.dk\/en\/wp-content\/uploads\/skulls-300x204.png\" alt=\"skulls\" width=\"300\" height=\"204\" \/><\/a><\/p>\n<p>(<a href=\"https:\/\/cran.r-project.org\/web\/packages\/heplots\/vignettes\/HE-examples.pdf\">Image source<\/a>)<\/p>\n<p>I calculated means and 95% confidence intervals for each group x measurement combination. It looks like this:<\/p>\n<p><a href=\"http:\/\/emilkirkegaard.dk\/en\/wp-content\/uploads\/egyptian_skull_sizes.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5934 size-large\" src=\"http:\/\/emilkirkegaard.dk\/en\/wp-content\/uploads\/egyptian_skull_sizes-1024x657.png\" alt=\"egyptian_skull_sizes\" width=\"720\" height=\"462\" \/><\/a><\/p>\n<p>There are no noteworthy changes across about 4000 years aside from perhaps the decrease in basialveolar length, which seems fairly unimportant in relation to brain size.<\/p>\n<p>Factor analysis of the 4 measurements do not reveal a general skull size factor which <a href=\"http:\/\/emilkirkegaard.dk\/en\/?p=5034\">was found for brain size<\/a>.<\/p>\n<pre id=\"rstudio_console_output\" class=\"GC5UO3EDPKB\" tabindex=\"0\">Factor Analysis using method =  minres\r\nCall: fa(r = d_skulls[-5])\r\nStandardized loadings (pattern matrix) based upon correlation matrix\r\n                       MR1      h2   u2 com\r\nmaximum_breadth      -0.20 3.8e-02 0.96   1\r\nbasibregmatic_height  0.33 1.1e-01 0.89   1\r\nbasialveolar_length   0.80 6.4e-01 0.36   1\r\nnasal_height          0.00 2.9e-06 1.00   1\r\n\r\n                MR1\r\nSS loadings    0.79\r\nProportion Var 0.20<\/pre>\n<p>Perhaps the measurements are too unreliable compared to the modern MRI.<\/p>\n<p><strong>Supplementary materials<\/strong><\/p>\n<p>The R code: https:\/\/gist.github.com\/Deleetdk\/6ee734db2292be83ab3c6a055c9adbf0<\/p>\n<p>The data is loaded from the R package <strong>ade4<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I often read statistics textbooks. In textbooks, they often use example datasets, some of which are interesting in themselves (e.g. the Boston dataset). In this case, I am reading An Introduction to Applied Multivariate Analysis with R. It features a dataset of Egyptian skulls spanning about 4000 years. Given the scholarly interest in dysgenics and [&hellip;]<\/p>\n","protected":false},"author":17,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2335],"tags":[2338,1987,2337,2336],"class_list":["post-5933","post","type-post","status-publish","format-standard","hentry","category-physiology","tag-ancient","tag-brain-size","tag-egyptian","tag-skull-size","entry"],"_links":{"self":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts\/5933","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/comments?post=5933"}],"version-history":[{"count":3,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts\/5933\/revisions"}],"predecessor-version":[{"id":5938,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts\/5933\/revisions\/5938"}],"wp:attachment":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/media?parent=5933"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/categories?post=5933"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/tags?post=5933"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}