DOCSLIB.ORG

Evo-Devo: the Evolution of a New Discipline

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evo-Devo: the Evolution of a New Discipline PERSPECTIVES Scientist 1 May (2000). Box 5 | European Parliament directive on patenting 12. Eisenberg R. S. Intellectual property issues in genomics. Trends Biotechnol. 14, 302–307 (1996). Directive 98/44/EC of the European Parliament and of the Council of the 6 July 1998 on the legal 13. US Code, title 35, § 102(a). 14. US Code, title 35, § 103. protection of biotechnological inventions, Official Journal L 213, 30/07/1998 p. 0013–0021 Article 5: 15. Parchomovsky, G. Publish or perish. Michigan Law Rev. • The human body, at the various stages of its formation and development, and the simple 98, 926–952 (2000). 16. Lichtman, D., Baker, S. & Kraus, K. Strategic disclosure in discovery of one of its elements, including the sequence or partial sequence of a gene, cannot the patent system. Vanderbilt Law Rev. (in the press). constitute patentable inventions. 17. Bishop, J. E. Plan may blow lid off secret gene research. Wall Street Journal 28 September (1994). • An element isolated from the human body or otherwise produced by means of a technical process, 18. In re Bell, 991 Federal Reporter, 2d series 781 (Court of including the sequence or partial sequence of a gene, may constitute a patentable invention, even if Appeals for the Federal Circuit, 1993). 19. In re Deuel, 51 Federal Reporter, 3d series 1552 (Court of the structure of that element is identical to that of a natural element. Appeals for the Federal Circuit, 1995). 20. Marshall, E. Drug firms to create public database of genetic • The industrial application of a sequence or a partial sequence of a gene must be disclosed mutations. Science 284, 406–407 (1999). in the patent application. 21. US Code, title 35, § 157(c). 22. US Code, title 35 § 102(e). 23. Shapiro, C. & Varian, H. R. Information Rules: A Strategic concern may motivate some institutions to ests might do more to enlighten public policy Guide to the Network Economy (Harvard Business School Press, Cambridge, Massachusetts, 1998). defer publication in precisely the circum- debates about the importance of the public 24. Venter, J. C. Clinton and Blair shouldn’t destroy our stances that it motivates other institutions to domain in genomics research than appeals to research. Wall Street Journal 21 March (2000). 25. Marshall, E. Talks of public–private deal end in acrimony. make prompt disclosure. The difference ethical imperatives. Science 287, 1723–1725 (2000). depends on whether they believe that pre- 26. Bentley, D. R. Genomic sequence data should be released Rebecca S. Eisenberg is the Robert & Barbara immediately and freely in the public domain. Science 274, empting future patents is good or bad. Apart Luciano Professor of Law at the University of 533–534 (1996). 27. Adams, M. D. & Venter, C. J. Should non-peer-reviewed from concern about preserving their own Michigan Law School, Ann Arbor, Michigan 48109, raw DNA sequence data be forced on the scientific patent rights, public research sponsors and USA. e-mail: [email protected] community? Science 274, 534–536 (1996). publicly funded research performers may 1. Venter, J. C. et al. Shotgun sequencing of the human Acknowledgements genome. Science 280, 1540–1542 (1998). This research has been supported by a grant from the United worry that premature public disclosure could 2. King R. T. Jr Code green: Gene quest will bring glory to States Department of Energy. prevent them from complying with their some; Incyte will stick with cash. The Wall Street Journal 10 February (2000). Links mandate under the Bayh–Dole Act to pro- 3. Healy, B. Special report on gene patenting. N. Engl. J. Med. 327, 664–667 (1992). mote technology transfer and product devel- 4. Eisenberg, R. S. Public research and private development. COMPANIES Celera | Monsanto | Merck | Incyte opment by patenting research results. Indeed, Virginia Law Rev. 82, 1663–1727 (1996). |Human Genome Sciences 5. Waterston, R. & Sulston, J. E. The Human Genome Project: this concern was cited by former NIH director Reaching the finish line. Science 287, 53–54 (1998). FURTHER INFORMATION Human Genome Bernadine Healy in support of the decision to 6. Marshall, E. Claim and counterclaim on the human Project | Joint statement by Bill Clinton and genome. Science 288, 242–243 (2000). Tony Blair | The SNP Consortium | The file patent applications on the first ESTs iden- 7. Nowak, R. The gold bug: Helicobacter pylori; claimed to tified by Craig Venter when he was at NIH25. be the first free-living organism genome fully sequenced. Bermuda rules | National Human Genome Science 267, 173–174 (1995). Research Institute policy on patenting of In fact, it does not seem that publication of 8. Wade, N. 10 Drug makers join in drive to find diseases’ human genomic sequence | Interim utility raw genomic DNA sequence will prevent the genetic roots. The New York Times 15 April (1999). 9. European Patent Convention, Article 54. guidelines and written description guidelines issuance of patents on genes that are subse- 10. US Code, title 35, § 102(b). 11. Palevitz, B. A. Rice genome gets a boost: private for Patent Examiners | European Parliament quently found to lie within that sequence sequencing effort yields rough draft for the public. The directive on patenting under United States law. The situation in Europe is less certain and awaits clarification of national laws in response to a 1998 directive of the European Parliament on the legal protec- OPINION tion of biotechnological inventions (BOX 5). Although the patent system has not yet resolved many of the legal issues that will determine what portions of the human Evo-devo: the evolution genome may be patented, for the time being there seems to be little threat that disclosure of of a new discipline the human genome in the public domain will leave future researchers who identify and char- Rudolf A. Raff acterize genes with nothing left to patent. The history of life documented in the fossil of development, and how the process Conclusion record shows that the evolution of of development itself biases or constrains Complex and interrelated strategies for complex organisms such as animals and evolution. A revolutionary synthesis of endowing the public domain are at work in the plants has involved marked changes in developmental biology and evolution is field of genomics. These strategies arise out of morphology, and the appearance of new in progress. the varied plans of different institutions for features. However, evolutionary change extracting value out of genomic information, occurs not by the direct transformation of Developmental and evolutionary biology complicated by the interplay of the public adult ancestors into adult descendants are two disciplines that explore morpholog- domain with the patent system. Public disclo- but rather when developmental processes ical change in organisms over time. sure of genomic information advances some produce the features of each generation However, the processes involved are differ- interests while harming others, with no simple in an evolving lineage. Therefore, ent. Development is genetically pro- distinction between the interests of public and evolution cannot be understood grammed and cyclical. Evolution is non- private institutions. Understanding these inter- without understanding the evolution programmed and contingent. Although a 74 | OCTOBER 2000 | VOLUME 1 www.nature.com/reviews/genetics PERSPECTIVES link between the two processes was recog- mental biologists. But palaeontology pro- phylogenetic distance, making genes identi- nized in the late nineteenth century, an vides insights available in no other way. For fied by developmental mutations most use- effective connection of evolutionary and example, the discovery that the earliest (fos- ful in comparisons of related taxa. developmental biology awaited the appear- sil) TETRAPODS had feet with eight toes rather ance of developmental data that contained a than five2 was a complete surprise, and was The contribution of phylogenetics strong and marked evolutionary signal. This important in providing us with a new view Evolutionary biology is comparative, and happened in the 1980s, when the growth of of what ancestral limbs were actually like, requires tracking events over long time developmental genetics established a link and for giving us clues as to how limb devel- frames, and across phylogeny. Although phy- between genes and development. As devel- opment evolved. logenetic relationships have not been regard- opmental regulatory genes were cloned and Finally, evolutionary biologists are faced ed as important for the study of develop- sequenced — notably those of the Hox gene with understanding how small genotypic mental mechanisms, they become crucial family, which are important in specification once we begin to consider the evolution of of the identity of insect segments — it was developmental processes3. New analytical realized that the same regulatory genes were “Development is methods provided by CLADISTICS and the shared by animals with different body plans avalanche of gene sequence data have revo- (for example, insects and vertebrates). More genetically programmed lutionized phylogeny. importantly, shared regulatory genes have and cyclical. Evolution Phylogeny imparts three important kinds conserved roles in development, which of information. First, we can determine the some have taken to indicate homologies in is non-programmed direction in which developmental features the development of body architecture and contingent.” are evolving. Second, knowing the diver- among different animal body plans1. gence times of branches in a tree allows evo- Developmental biology has once again lution rates to be inferred. (There is, at pre- become relevant to understanding both modificationsEPIGENETICS are translated into phenotypic sent, controversy about using extrapolations evolutionary mechanisms and the patterns changes during evolution, and how micro- of rates of gene evolution to determine of evolutionary history that are revealed by evolutionary changes contribute to the important divergences that pre-date visible palaeontology and PHYLOGENETIC studies. MACRO-EVOLUTIONARY events on the timescale fossil evidence; the divergence among ani- observed in the fossil record.
Load more

Recommended publications
  • Role of Hox Genes in Regulating Digit Patterning ROCÍO PÉREZ-GÓMEZ, ENDIKA HARO, MARC FERNÁNDEZ-GUERRERO, MARÍA F
    Int. J. Dev. Biol. 62: 797-805 (2018) https://doi.org/10.1387/ijdb.180200mr www.intjdevbiol.com Role of Hox genes in regulating digit patterning ROCÍO PÉREZ-GÓMEZ, ENDIKA HARO, MARC FERNÁNDEZ-GUERRERO, MARÍA F. BASTIDA and MARÍA A. ROS* Instituto de Biomedicina y Biotecnología de Cantabria, CSIC–SODERCAN Universidad de Cantabria, Santander, Spain ABSTRACT The distal part of the tetrapod limb, the autopod, is characterized by the presence of digits. The digits display a wide diversity of shapes and number reflecting selection pressure for functional adaptation. Despite extensive study, the different aspects of digit patterning, as well as the factors and mechanisms involved are not completely understood. Here, we review the evidence implicating Hox proteins in digit patterning and the interaction between Hox genes and the Sonic hedgehog/Gli3 pathway, the other major regulator of digit number and identity. Currently, it is well accepted that a self-organizing Turing-type mechanism underlies digit patterning, this being understood as the establishment of an iterative arrangement of digit/interdigit in the hand plate. We also discuss the involvement of 5’ Hox genes in regulating digit spacing in the digital plate and therefore the number of digits formed in this self-organizing system. KEY WORDS: limb development, Hox gene, digit patterning, Shh, Gli3 Introduction and Meyer, 2015). The digits are crucial elements for the function of the limb. They The basic plan of the tetrapod limb includes three distinct can be viewed as serial identical structures arranged along the proximo-distal (PD) segments: the stylopod (arm), the zeugopod antero-posterior (AP) axis of the autopod, thumb to little finger, or (forearm) and the autopod (hand/foot).
    [Show full text]
  • Genomics and Its Impact on Science and Society: the Human Genome Project and Beyond
    DOE/SC-0083 Genomics and Its Impact on Science and Society The Human Genome Project and Beyond U.S. Department of Energy Genome Research Programs: genomics.energy.gov A Primer ells are the fundamental working units of every living system. All the instructions Cneeded to direct their activities are contained within the chemical DNA (deoxyribonucleic acid). DNA from all organisms is made up of the same chemical and physical components. The DNA sequence is the particular side-by-side arrangement of bases along the DNA strand (e.g., ATTCCGGA). This order spells out the exact instruc- tions required to create a particular organism with protein complex its own unique traits. The genome is an organism’s complete set of DNA. Genomes vary widely in size: The smallest known genome for a free-living organism (a bac- terium) contains about 600,000 DNA base pairs, while human and mouse genomes have some From Genes to Proteins 3 billion (see p. 3). Except for mature red blood cells, all human cells contain a complete genome. Although genes get a lot of attention, the proteins DNA in each human cell is packaged into 46 chro- perform most life functions and even comprise the mosomes arranged into 23 pairs. Each chromosome is majority of cellular structures. Proteins are large, complex a physically separate molecule of DNA that ranges in molecules made up of chains of small chemical com- length from about 50 million to 250 million base pairs. pounds called amino acids. Chemical properties that A few types of major chromosomal abnormalities, distinguish the 20 different amino acids cause the including missing or extra copies or gross breaks and protein chains to fold up into specific three-dimensional rejoinings (translocations), can be detected by micro- structures that define their particular functions in the cell.
    [Show full text]
  • Phylogeny of a Rapidly Evolving Clade: the Cichlid Fishes of Lake Malawi
    Proc. Natl. Acad. Sci. USA Vol. 96, pp. 5107–5110, April 1999 Evolution Phylogeny of a rapidly evolving clade: The cichlid fishes of Lake Malawi, East Africa (adaptive radiationysexual selectionyspeciationyamplified fragment length polymorphismylineage sorting) R. C. ALBERTSON,J.A.MARKERT,P.D.DANLEY, AND T. D. KOCHER† Department of Zoology and Program in Genetics, University of New Hampshire, Durham, NH 03824 Communicated by John C. Avise, University of Georgia, Athens, GA, March 12, 1999 (received for review December 17, 1998) ABSTRACT Lake Malawi contains a flock of >500 spe- sponsible for speciation, then we expect that sister taxa will cies of cichlid fish that have evolved from a common ancestor frequently differ in color pattern but not morphology. within the last million years. The rapid diversification of this Most attempts to determine the relationships among cichlid group has been attributed to morphological adaptation and to species have used morphological characters, which may be sexual selection, but the relative timing and importance of prone to convergence (8). Molecular sequences normally these mechanisms is not known. A phylogeny of the group provide the independent estimate of phylogeny needed to infer would help identify the role each mechanism has played in the evolutionary mechanisms. The Lake Malawi cichlids, however, evolution of the flock. Previous attempts to reconstruct the are speciating faster than alleles can become fixed within a relationships among these taxa using molecular methods have species (9, 10). The coalescence of mtDNA haplotypes found been frustrated by the persistence of ancestral polymorphisms within populations predates the origin of many species (11). In within species.
    [Show full text]
  • From the Human Genome Project to Genomic Medicine a Journey to Advance Human Health
    From the Human Genome Project to Genomic Medicine A Journey to Advance Human Health Eric Green, M.D., Ph.D. Director, NHGRI The Origin of “Genomics”: 1987 Genomics (1987) “For the newly developing discipline of [genome] mapping/sequencing (including the analysis of the information), we have adopted the term GENOMICS… ‘The Genome Institute’ Office for Human Genome Research 1988-1989 National Center for Human Genome Research 1989-1997 National Human Genome Research Institute 1997-present NHGRI: Circa 1990-2003 Human Genome Project NHGRI Today: Characteristic Features . Relatively young (~28 years) . Relatively small (~1.7% of NIH) . Unusual historical origins (think ‘Human Genome Project’) . Emphasis on ‘Team Science’ (think managed ‘consortia’) . Rapidly disseminating footprint (think ‘genomics’) . Novel societal/bioethics research component (think ‘ELSI’) . Over-achievers for trans-NIH initiatives (think ‘Common Fund’) . Vibrant (and large) Intramural Research Program A Quarter Century of Genomics Human Genome Sequenced for First Time by the Human Genome Project Genomic Medicine An emerging medical discipline that involves using genomic information about an individual as part of their clinical care (e.g., for diagnostic or therapeutic decision- making) and the other implications of that clinical use The Path to Genomic Medicine ? Human Realization of Genome Genomic Project Medicine Nature Nature Base Pairs to Bedside 2003 Heli201x to 1Health A Quarter Century of Genomics Human Genome Sequenced for First Time by the Human Genome Project
    [Show full text]
  • Next-Generation Sequencing
    Tinhofer et al. Radiation Oncology (2015) 10:183 DOI 10.1186/s13014-015-0481-x REVIEW Open Access Next-generation sequencing: hype and hope for development of personalized radiation therapy? Ingeborg Tinhofer1,2*, Franziska Niehr1,2, Robert Konschak1,2, Sandra Liebs2, Matthias Munz3, Albrecht Stenzinger4, Wilko Weichert4,5, Ulrich Keilholz6 and Volker Budach1,2 Abstract The introduction of next-generation sequencing (NGS) in the field of cancer research has boosted worldwide efforts of genome-wide personalized oncology aiming at identifying predictive biomarkers and novel actionable targets. Despite considerable progress in understanding the molecular biology of distinct cancer entities by the use of this revolutionary technology and despite contemporaneous innovations in drug development, translation of NGS findings into improved concepts for cancer treatment remains a challenge. The aim of this article is to describe shortly the NGS platforms for DNA sequencing and in more detail key achievements and unresolved hurdles. A special focus will be given on potential clinical applications of this innovative technique in the field of radiation oncology. Introduction and Wong et al. [11]. We will instead focus on key achieve- Recent technological advances in DNA sequencing with ments in cancer genetics and potential clinical applications of greater speed and resolution at lower costs has provided this innovative technique in the field of radiation oncology. new insights in cancer genetics. The next-generation se- quencing (NGS) technology is tremendously facilitating the in-depth genome-wide search for genetic alterations The advantages of NGS which might significantly contribute to aggressive and/or Next-generation sequencing has rapidly been evolv- treatment-resistant phenotypes of cancers, thereby es- ing within the last decade [10].
    [Show full text]
  • Gabriel Dover)
    Dear Mr Darwin (Gabriel Dover) Home | Intro | About | Feedback | Prev | Next | Search Steele: Lamarck's Was Signature Darwin Wrong? Molecular Drive: the Third Force in evolution Geneticist Gabriel Dover claims that there is a third force in evolution: 'Molecular Drive' beside natural selection and neutral drift. Molecular drive is operationally distinct from natural selection and neutral drift. According to Dover it explains biological phenomena, such as the 700 copies of a ribosomal RNA gene and the origin of the 173 legs of the centipede, which natural selection and neutral drift alone cannot explain. by Gert Korthof version 1.3 24 Mar 2001 Were Darwin and Mendel both wrong? Molecular Drive is, according to Dover, an important factor in evolution, because it shapes the genomes and forms of organisms. Therefore Neo-Darwinism is incomplete without Molecular Drive. It is no wonder that the spread of novel genes was ascribed to natural selection, because it was the only known process that could promote the spread of novel genes. Dover doesn't reject the existence of natural selection but points out cases where natural selection clearly fails as a mechanism. Molecular drive is a non-Darwinian mechanism because it is independent of selection. We certainly need forces in evolution, since natural selection itself is not a force. It is the passive outcome of other processes. It is not an active process, notwithstanding its name. Natural selection as an explanation is too powerful for its own good. Molecular drive is non-Mendelian because some DNA segments are multiplied disproportional. In Mendelian genetics genes are present in just two copies (one on the maternal and one on the paternal chromosome).
    [Show full text]
  • Homeobox Gene Expression Profile in Human Hematopoietic Multipotent
    Leukemia (2003) 17, 1157–1163 & 2003 Nature Publishing Group All rights reserved 0887-6924/03 $25.00 www.nature.com/leu Homeobox gene expression profile in human hematopoietic multipotent stem cells and T-cell progenitors: implications for human T-cell development T Taghon1, K Thys1, M De Smedt1, F Weerkamp2, FJT Staal2, J Plum1 and G Leclercq1 1Department of Clinical Chemistry, Microbiology and Immunology, Ghent University Hospital, Ghent, Belgium; and 2Department of Immunology, Erasmus Medical Center, Rotterdam, The Netherlands Class I homeobox (HOX) genes comprise a large family of implicated in this transformation proces.14 The HOX-C locus transcription factors that have been implicated in normal and has been primarily implicated in lymphomas.15 malignant hematopoiesis. However, data on their expression or function during T-cell development is limited. Using degener- Hematopoietic cells are derived from stem cells that reside in ated RT-PCR and Affymetrix microarray analysis, we analyzed fetal liver (FL) in the embryo and in the adult bone marrow the expression pattern of this gene family in human multipotent (ABM), which have the unique ability to self-renew and thereby stem cells from fetal liver (FL) and adult bone marrow (ABM), provide a life-long supply of blood cells. T lymphocytes are a and in T-cell progenitors from child thymus. We show that FL specific type of hematopoietic cells that play a major role in the and ABM stem cells are similar in terms of HOX gene immune system. They develop through a well-defined order of expression, but significant differences were observed between differentiation steps in the thymus.16 Several transcription these two cell types and child thymocytes.
    [Show full text]
  • The Polyp and the Medusa Life on the Move
    The Polyp and the Medusa Life on the Move Millions of years ago, unlikely pioneers sparked a revolution. Cnidarians set animal life in motion. So much of what we take for granted today began with Cnidarians. FROM SHAPE OF LIFE The Polyp and the Medusa Life on the Move Take a moment to follow these instructions: Raise your right hand in front of your eyes. Make a fist. Make the peace sign with your first and second fingers. Make a fist again. Open your hand. Read the next paragraph. What you just did was exhibit a trait we associate with all animals, a trait called, quite simply, movement. And not only did you just move your hand, but you moved it after passing the idea of movement through your brain and nerve cells to command the muscles in your hand to obey. To do this, your body needs muscles to move and nerves to transmit and coordinate movement, whether voluntary or involuntary. The bit of business involved in making fists and peace signs is pretty complex behavior, but it pales by comparison with the suites of thought and movement associated with throwing a curve ball, walking, swimming, dancing, breathing, landing an airplane, running down prey, or fleeing a predator. But whether by thought or instinct, you and all animals except sponges have the ability to move and to carry out complex sequences of movement called behavior. In fact, movement is such a basic part of being an animal that we tend to define animalness as having the ability to move and behave.
    [Show full text]
  • A Short History of DNA Technology 1865 - Gregor Mendel the Father of Genetics
    A Short History of DNA Technology 1865 - Gregor Mendel The Father of Genetics The Augustinian monastery in old Brno, Moravia 1865 - Gregor Mendel • Law of Segregation • Law of Independent Assortment • Law of Dominance 1865 1915 - T.H. Morgan Genetics of Drosophila • Short generation time • Easy to maintain • Only 4 pairs of chromosomes 1865 1915 - T.H. Morgan •Genes located on chromosomes •Sex-linked inheritance wild type mutant •Gene linkage 0 •Recombination long aristae short aristae •Genetic mapping gray black body 48.5 body (cross-over maps) 57.5 red eyes cinnabar eyes 67.0 normal wings vestigial wings 104.5 red eyes brown eyes 1865 1928 - Frederick Griffith “Rough” colonies “Smooth” colonies Transformation of Streptococcus pneumoniae Living Living Heat killed Heat killed S cells mixed S cells R cells S cells with living R cells capsule Living S cells in blood Bacterial sample from dead mouse Strain Injection Results 1865 Beadle & Tatum - 1941 One Gene - One Enzyme Hypothesis Neurospora crassa Ascus Ascospores placed X-rays Fruiting on complete body medium All grow Minimal + amino acids No growth Minimal Minimal + vitamins in mutants Fragments placed on minimal medium Minimal plus: Mutant deficient in enzyme that synthesizes arginine Cys Glu Arg Lys His 1865 Beadle & Tatum - 1941 Gene A Gene B Gene C Minimal Medium + Citruline + Arginine + Ornithine Wild type PrecursorEnz A OrnithineEnz B CitrulineEnz C Arginine Metabolic block Class I Precursor OrnithineEnz B CitrulineEnz C Arginine Mutants Class II Mutants PrecursorEnz A Ornithine
    [Show full text]
  • Animal Origins and the Evolution of Body Plans 621
    Animal Origins and the Evolution 32 of Body Plans In 1822, nearly forty years before Darwin wrote The Origin of Species, a French naturalist, Étienne Geoffroy Saint-Hilaire, was examining a lob- ster. He noticed that when he turned the lobster upside down and viewed it with its ventral surface up, its central nervous system was located above its digestive tract, which in turn was located above its heart—the same relative positions these systems have in mammals when viewed dorsally. His observations led Geoffroy to conclude that the differences between arthropods (such as lobsters) and vertebrates (such as mammals) could be explained if the embryos of one of those groups were inverted during development. Geoffroy’s suggestion was regarded as preposterous at the time and was largely dismissed until recently. However, the discovery of two genes that influence a sys- tem of extracellular signals involved in development has lent new support to Geof- froy’s seemingly outrageous hypothesis. Genes that Control Development A A vertebrate gene called chordin helps to establish cells on one side of the embryo human and a lobster carry similar genes that control the development of the body as dorsal and on the other as ventral. A probably homologous gene in fruit flies, called axis, but these genes position their body sog, acts in a similar manner, but has the opposite effect. Fly cells where sog is active systems inversely. A lobster’s nervous sys- become ventral, whereas vertebrate cells where chordin is active become dorsal. How- tem runs up its ventral (belly) surface, whereas a vertebrate’s runs down its dorsal ever, when sog mRNA is injected into an embryo (back) surface.
    [Show full text]
  • Giraffe Stature and Neck Elongation: Vigilance As an Evolutionary Mechanism
    biology Review Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism Edgar M. Williams Faculty of Life Sciences and Education, University of South Wales, Wales CF37 1DL, UK; [email protected]; Tel.: +44-1443-483-893 Academic Editor: Chris O’Callaghan Received: 1 August 2016; Accepted: 7 September 2016; Published: 12 September 2016 Abstract: Giraffe (Giraffa camelopardalis), with their long neck and legs, are unique amongst mammals. How these features evolved is a matter of conjecture. The two leading ideas are the high browse and the sexual-selection hypotheses. While both explain many of the characteristics and the behaviour of giraffe, neither is fully supported by the available evidence. The extended viewing horizon afforded by increased height and a need to maintain horizon vigilance, as a mechanism favouring the evolution of increased height is reviewed. In giraffe, vigilance of predators whilst feeding and drinking are important survival factors, as is the ability to interact with immediate herd members, young and male suitors. The evidence regarding giraffe vigilance behaviour is sparse and suggests that over-vigilance has a negative cost, serving as a distraction to feeding. In woodland savannah, increased height allows giraffe to see further, allowing each giraffe to increase the distance between its neighbours while browsing. Increased height allows the giraffe to see the early approach of predators, as well as bull males. It is postulated that the wider panorama afforded by an increase in height and longer neck has improved survival via allowing giraffe to browse safely over wider areas, decreasing competition within groups and with other herbivores.
    [Show full text]
  • The Cambrian Explosion: a Big Bang in the Evolution of Animals
    The Cambrian Explosion A Big Bang in the Evolution of Animals Very suddenly, and at about the same horizon the world over, life showed up in the rocks with a bang. For most of Earth’s early history, there simply was no fossil record. Only recently have we come to discover otherwise: Life is virtually as old as the planet itself, and even the most ancient sedimentary rocks have yielded fossilized remains of primitive forms of life. NILES ELDREDGE, LIFE PULSE, EPISODES FROM THE STORY OF THE FOSSIL RECORD The Cambrian Explosion: A Big Bang in the Evolution of Animals Our home planet coalesced into a sphere about four-and-a-half-billion years ago, acquired water and carbon about four billion years ago, and less than a billion years later, according to microscopic fossils, organic cells began to show up in that inert matter. Single-celled life had begun. Single cells dominated life on the planet for billions of years before multicellular animals appeared. Fossils from 635,000 million years ago reveal fats that today are only produced by sponges. These biomarkers may be the earliest evidence of multi-cellular animals. Soon after we can see the shadowy impressions of more complex fans and jellies and things with no names that show that animal life was in an experimental phase (called the Ediacran period). Then suddenly, in the relatively short span of about twenty million years (given the usual pace of geologic time), life exploded in a radiation of abundance and diversity that contained the body plans of almost all the animals we know today.
    [Show full text]