Really loved this book. Have always been fascinated in side shows and in diversity and what the implications for individuals with mutations would be. This is a really scientific book, but if you stick with it, it is well worth it. ( )

Disclaimer: this book was published in 2003, so of course there are portions out of date (the chapter on gender for example) But otherwise this was a fascinating tour through the world of biology and genetics!

The author makes a valid point throughout that "mutant" genes should neither be gawked at nor ignored. And they don't just "happen." Nearly all of the conditions mentioned are caused by a mutation in a protein. But these mutations could be a result of nutritional deficiency, chemical poison, environmental hazard, etc. For example, the (now banned) use of Thalidomide for morning sickness! Some mutations can be traced back hundreds of years because of a unique physical trait. The author also discusses the darker treatment of those who were considered "monsters" or "freaks." Courts and princes collected them, naturalists catalogued them and theologians turned them into religious propaganda. It was thought that a pregnant woman could cause deformity in her child if she looked at an "unsightly" thing. At Auschwitz, Elizabeth Ovitz and her family (among many others) were tortured under Mengele, who was never tried for his crimes!

Among those mentioned are Ritta and Christina Parodi, Harry Eastlack (who's skeleton I saw at the Mutter Museum!), Clara and Altagracia Rodriguez, and more famous names like Charles Byrne, Eng and Chang, Joseph Boruwlaski and Henri de Toulouse-Lautrec. I learned about Kartagener's Syndrome, the "sonic hedgehog mutation" (it's true!), Cleppie Bells, BMPs, Hoxd13, cyclopia, osteopetrosis, the noggin molecule, sirenomelia and Robert's Syndrome just to name a few. And explaining these mutations in layman's terms is no easy feat. It's not perfect, as the study of the human body is never ending, but I gained an incredible amount of new information and starting points for more! ( )

Mutants: On Genetic Variety and the Human body discusses exactly what it says it does. The physical effects of altered or missing genes on the various parts of the human body are discussed in some detail. Some of the "mutations" discussed in the book include conjoined twins, mermaid syndrome, cyclops syndrome, pygmies, giants, hermaphrodites, skin and skeletal issues and aging. This book is extremely interesting, without being distasteful or gory. The science (real science!!) is understandable but not overly simplified. Black and white illustrations are included regularly.


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An interesting, fascinating book about the mutations of the human genes and its effects, sometimes only strange, sometimes terrifying. ( )

Very good, if a little creepy. Author Armand Marie Leroi treats the subject of human body variation (we’re talking things like conjoined twins, not eye color) with a mixture of compassion and intellectual curiosity that would make me happy to deal with him if I had two heads. Both of us, in fact.


Conjoined twins (“Siamese twins” in less politically correct times) result from fusion of embryonic disks very early in development. The details are fascinating: 77% of conjoined twins are both female; it’s possible, although rare, to have conjoined twins that are not monozygotic (i.e., not “identical”), demonstrating that at least some of the time they are the result of embryo fusion rather than splitting. In 50% of cases, one twin is “inverted” (the internal organs are reversed left-right). This last observation leads Leroi to discuss Kartagener’s syndrome – organ inversion in single births (about 1:8500). People with Kartagener’s syndrome generally have a poor sense of smell, and men born with it are sterile. What these things have in common is defective cilia; and it turns out that there’s a small group of mesodermal cells in the very early embryo that have cilia and provide a very weak current in the amniotic fluid. The current allows the developing embryo to distinguish left from right, and if the cilia are nonfunctional it goes wrong half the time.


Leroi continues with a discussion of homeobox genes and their role in setting up bilateral symmetry in the body. I was surprised to discover that about 10% of people have an extra rib – odds are that someone here does. The extra can come in a variety of ways; a cervical vertebra can get the wrong signal and develop ribs it isn’t supposed to (I know someone with that; she had to have them removed as they were causing “thoracic outlet syndrome", a sort of carpal tunnel of the shoulders). I also know somebody with extra ribs because he’s go an entire extra back vertebra, not discovered until he tried to join the National Guard. The discussion of homeobox genes helped me see what Martin Lockley was getting a when he talked about them as the reason for the small forelimbs of Tyrannosaurus rex in a book reviewed earlier; I still don’t agree with him but it makes a little more sense now.


Then there are various limb defects - polydactyly, “cleppies” with claw-like hands, phocomelia, and so on. Interestingly, people with defective limbs tend to have defective genitalia as well, and Leroi notes that the folk-wisdom correlation between foot size and penis size is actually true (although weak).


The chapter on bone variations has some unpleasant illustrations: the skeleton of the unfortunate Harry Eastlake, who suffered from a condition that caused continuous and random bone growth, and a family of Transylvanian Jews with pseudoachondroplasia who ended up surviving Auschwitz because they were favorites of Joseph Mengele. Growth conditions – pygmies, giants, castrati, and Proteus (Elephant Man) syndrome are caused by various changes in genes that make growth factor hormones. Castrati were tall because they lacked estrogen (usually thought of as a female hormone but in fact produced in small quantities by men); apparently the presence of estrogen is necessary to halt growth at adulthood, and thus castrati never stop growing - they have the “bone age” of teenagers all their lives. (Sounds like a good handle for an Aaron Elkins mystery). Interestingly, there are several perfectly masculine men known with the same condition; rather than lacking estrogen, they lack estrogen receptors. Height has profound cultural associations; at the time the book was published (2003), the taller of two US presidential candidates had won election 40 out of 43 times; women of all cultures surveyed preferred mates at last two inches taller than they are, and in the academic world full professors at US universities average ¾ inches taller than assistant professors. There are, of course, ethical implications for the use of human growth hormone that are mentioned but not extensively discussed.


The chapter on gender variation complements the Joan Roughgarden work (Evolution’s Rainbow) I reviewed a while back. Leroi discusses paradoxical “sex-reversed” men and women - XX men and XY women. Although the genes for genital development are on the X chromosome, there’s a small region (SRY, Sex-determining Region) on the Y chromosome that actually triggers male genitalia. Once in a great while this region gets translocated on to an X chromosome, leading to someone that’s genetically male but chromosomally female. Similar, if the region’s defective, an XY person remains female. Interestingly, the chromosomal layout in birds and reptiles is reversed; it’s males that have two identical sex chromosomes and females that have different ones (called W and Z). This suggests some time in mammalian ancestry a “reversed sex” translocation like this became the normal condition instead of a genetic defect.


The chapter on skin variants discusses albinism, piebaldism, and whole-body hairiness. Leroi makes an interesting note on redheads; they lack a eumelanin receptor. This takes him down the path of considering whether redheads are exhibiting a simple genetic polymorphism or a mutation (and a possible deleterious one at that). There is no single “redhead gene”; instead there are about 30 different variants of the MC1R gene that codes for phaeomelanin rather than eumelanin. Thus any given variant of MC1R is vanishingly rare, and Leroi concludes it’s a mutation rather than a polymorphism (albeit one that’s often pleasant to look at).


The final chapter, appropriately, is about the genetics of aging. The iron rule of natural selection dictates that deleterious mutations that don't take effect until after reproductive years will not be selected against, with Huntington’s disease (and now likely Alzheimer’s disease) as the classic examples. Leroi extends this to the entire aging process; our lives end because of accumulation of mutations that are not subject to selection.


Very interesting and recommended. There’s an extensive bibliography and, as mentioned, abundant if slightly creepy illustrations. One nit to pick; it would have been nice if Leroi had shown some illustrations of the areas in a developing embryo affected by some of the mutations discussed, especially things like defective neural tube development. ( )