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Rewriting textbooks: Can we tell the sex of a dinosaur by the shape of its bones?

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Mallon with dino skulls/Dan Smythe, Canadian Museum of Nature

Maybe not. From ScienceDaily:

Dr. Jordan Mallon, a dinosaur specialist at the museum, argues instead that the fossil evidence for these distinctions is inconclusive and, as a result, it might be time to “rewrite the textbooks.” His report, published today in the online journal Paleobiology, focusses on the biological principle of sexual dimorphism, where males and females of a species can be distinguished based on physical characteristics other than sexual organs.

“I’m not saying that dinosaurs were not dimorphic, but I am saying that there’s no existing fossil evidence to suggest that they were. The jury is still out,” says Mallon.

Mallon made his assessment by revisiting previous studies attributing sexual dimorphism to dinosaurs. The problem, he explains, is that some of those studies not only relied on small sample sizes, but, more importantly, they did not properly analyze the statistical data, which led to invalid conclusions. (public access) Paper. – Jordan C. Mallon. Recognizing sexual dimorphism in the fossil record: lessons from nonavian dinosaurs. Paleobiology, 2017; 1 DOI: 10.1017/pab.2016.51 More.

Would preserved soft tissue help? As noted earlier, the exact role of sex as a strategy for procreation of complex life forms is unclear. Generally speaking, they use sexual reproduction but they get there by a variety of paths.

See also: Could a lamprey’s sex depend on food availability? Sex is a bit of a puzzle because it is a goal on which life forms seem to converge by many different ways. This one is different but logical.

And

Evolution appears to converge on goals—but in Darwinian terms, is that possible?

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2 Replies to “Rewriting textbooks: Can we tell the sex of a dinosaur by the shape of its bones?

  1. 1
    Dionisio says:

    Rewriting textbooks?

    Check this out:

    http://www.amazon.com/s/ref=nb.....Caps%2C240

    Year Edition
    2013 9th
    2008 8th
    2003 7th
    2098 6th

    Keith L. Moore
    T.V.N. Persaud

    This first paragraph of the introduction, which appeared in the 6th and 7th editions, was removed from the 8th edition and beyond.

    “Interest in human development before birth is widespread, largely because of curiosity about our beginnings and the desire to improve the quality of life. The intricate processes by which a baby develops from a single cell are miraculous, and few events are more exciting than a mother’s viewing of her embryo during an ultrasound examination. The adaptation of a newborn infant to its new environment is also exhilarating to witness.”

    · Series: Developing Human: Clinically Oriented Embryology
    · Paperback: 544 pages
    · Publisher: Saunders; 7th edition (January 25, 2003)
    · Language: English
    · ISBN-10: 0721694128
    · ISBN-13: 978-0721694122
    · Product Dimensions: 10.6 x 8.5 x 0.7 inches
    · Shipping Weight: 3.1 pounds

    · Paperback: 536 pages
    · Publisher: Saunders; 8th edition (September 19, 2007)
    · Language: English
    · ISBN-10: 1416037063
    · ISBN-13: 978-1416037064
    · Product Dimensions: 0.7 x 8.5 x 10.8 inches
    · Shipping Weight: 2.2 pounds

    · Paperback: 560 pages
    · Publisher: Saunders; 9th edition (December 19, 2011)
    · Language: English
    · ISBN-10: 1437720021
    · ISBN-13: 978-1437720020
    · Product Dimensions: 10.8 x 8.4 x 0.9 inches
    · Shipping Weight: 2.8 pounds

    I have the 6th edition on my bookshelf.

    Apparently the authors of the referred textbook are publicly known for their theological beliefs. However, perhaps it was not known to all until after the 7th edition of the book was out. Once the censorship police learned about the authors’ theological beliefs, the offending paragraph got removed from the following editions. This is speculation, because I don’t know the real story behind this obvious censorship case.

    I don’t know if there were additional editions after the 9th.

    Maybe the authors themselves changed their minds and decided to remove the first paragraph after the 7th edition?

    PS. Just confirmed there was a 10th edition.

    The Developing Human: Clinically Oriented Embryology, 10eApr 20, 2015
    by Keith L. Moore BA MSc PhD DSc FIAC FRSM FAAA and T. V. N. Persaud MD PhD DSc FRCPath (Lond.) FAAA

  2. 2
    Dionisio says:

    The Developing Human Being
    By Keith Moore, and T.V.N. Persaud
    7th edition, 2003

    Paperback: 560 pages
    Publisher: Saunders; 10 edition (April 20, 2015)
    Language: English
    ISBN-10: 0323313388
    ISBN-13: 978-0323313384
    Product Dimensions: 1 x 8.5 x 10.8 inches
    Shipping Weight: 3.1 pounds

    From an introductory definition section:

    “Human development is a continuous process that begins when an oocyte (ovum) from a female is fertilized by a sperm (spermatozoon) from a male. Cell division, cell migration, programmed cell death, differentiation, growth, and cell rearrangement transform the fertilized oocyte, a highly specialized, totipotent cell – a zygote – into a multicellular human being. Although most developmental changes occur during the embryonic and fetal periods, important changes occur during later periods of development: infancy, childhood, adolescence, and early adulthood.

    Development does not stop at birth. Important changes, in addition to growth, occur after birth (e.g., development of teeth and female breasts). The brain triples in weight between birth and 16 years; most developmental changes are completed by the age of 25. Although it is customary to divide human development into prenatal (before birth) and postnatal (after birth) periods, birth is merely a dramatic event during development resulting in a change in environment.” (p. 2)

    “Zygote. This cell results from the union of an oocyte and a sperm during fertilization. A zygote is the beginning of a new human being (i.e., an embryo).” (p. 2)

    “Embryo. The developing human during its early stages of development. The embryonic period extends to the end of the eighth week (56 days), by which time the beginnings of all major structures are present.” (p. 3)

    From chapter 2: “The Beginning of Human Development: First Week”

    First sentence of the Chapter: “Human development begins at fertilization when a male gamete or sperm (spermatozoon) unites with a female gamete or oocyte (ovum) to form a single cell – a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual.” (p. 16)

    “Studies on early stages of development indicate that human oocytes are usually fertilized with 12 hours after ovulation. In vitro observations have shown that the oocyte cannot be fertilized after 24 hours and this it degenerates shortly thereafter.” [This would buttress our argument that sperm and ovum by themselves are parts of the parents and not entire beings. That there is a substantial change between gametes and zygotes.] (p. 31)

    “The zygote is genetically unique because half of its chromosomes come from the mother and half from the father. The zygote contains a new combination of chromosomes that is different from that in the cells of either of the parents.” (p. 33)

    “Cleavage consists of repeated mitotic divisions of the zygote, resulting in a rapid increase in the number of cells. The embryonic cells – blastomeres – become smaller with each cleavage division. First the zygote divides into two blastomores, which then divide into four blastomores, either blastomeres, and so on.” (p. 36-37) [We can use the cleavage discussion to show that now the embryo is operating on its own and developing.]

    Copied from
    https://www.princeton.edu/~prolife/articles/embryoquotes.html

    It would be interesting to find whose decision was to remove the first paragraph from the introduction?

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