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The ''Rhynia'' plant was small and stick-like, with simple [[Dichotomy|dichotomously]] branching stems without leaves, each tipped by a [[sporangium]]. The simple form echoes that of the [[sporophyte]] of [[mosses]], and it has been shown that ''Rhynia'' had an [[alternation of generations]], with a corresponding [[gametophyte]] in the form of crowded tufts of diminutive stems only a few millimetres in height.<ref name="Kerpetal2004">{{cite journal |last1=Kerp |first1=Hans |last2=Trewin |first2=Nigel H. |last3=Hass |first3=Hagen |year=2003 |title=New gametophytes from the Early Devonian Rhynie chert |journal=Transactions of the Royal Society of Edinburgh: Earth Sciences |volume=94 |issue=4 |pages=411–428 |doi=10.1017/S026359330000078X |issn=0080-4568 |ref=harv}}</ref> ''Rhynia'' thus falls midway between mosses and early vascular plants like [[fern]]s and [[Lycopodiopsida|clubmoss]]es. From a carpet of moss-like gametophytes, the larger ''Rhynia'' sporophytes grew much like simple clubmosses, spreading by means of horizontal growing stems growing [[rhizoid]]s that anchored the plant to the substrate. The unusual mix of moss-like and vascular traits and the extreme structural simplicity of the plant had huge implications for botanical understanding.<ref>{{harvnb|Andrews|1967|p=32}}</ref>
==Misunderstandings==
<!-- Do not turn this section into a discussion of anti-evolution arguments. There are more appropriate articles for that. Even mentioning arguments by creationists is undue weight. -->
[[File:Human pidegree.jpg|thumb|right|The human pedigree back to [[amoeba]] shown as a reinterpreted [[Great chain of being|chain of being]] with living and fossil animals. From G. Avery's critique of [[Ernst Haeckel]], 1873.]]
[[File:Pithecanthropus-erectus.jpg|thumb|left|"[[Java Man]]" or ''Pithecanthropus erectus'' (now ''[[Homo erectus]]''), the original "missing link" found in Java in 1891–92.]]
<!-- The term "missing link" refers back to the originally static pre-evolutionary concept of the [[great chain of being]], a [[Deism|deist]] idea that all existence is linked, from the lowest [[dirt]], through the living [[kingdom (biology)|kingdoms]] to angels and finally to God.{{sfn|Lovejoy|1936}}--> The idea of all living things being linked through some sort of transmutation process predates Darwin's theory of evolution. [[Jean-Baptiste Lamarck]] envisioned that life iswas generated constantly in the form of the simplest creatures constantly, and then strivestrove [[Orthogenesis|towards complexity and perfection]] (i.e. humans) through a progressive series of lower forms.<ref>{{harvnb|Lamarck|1815–1822}}</ref> In his view, lower animals were simply newcomers on the evolutionary scene.<ref>{{cite journal |last=Appel |first=Toby A. |date=Fall 1980 |title=Henri De Blainville and the Animal Series: A Nineteenth-Century Chain of Being |journal=Journal of the History of Biology |volume=13 |issue=2 |pages=291–319 |doi=10.1007/BF00125745 |jstor=4330767 |s2cid=83708471 |issn=0022-5010 |ref=harv}}</ref>
After ''On the Origin of Species'', the idea of "lower animals" representing earlier stages in evolution lingered, as demonstrated in [[Ernst Haeckel]]'s figure of the human pedigree.{{sfn|Haeckel|2011|p=216}} While the vertebrates were then seen as forming a sort of evolutionary sequence, the various [[class (biology)|classes]] were distinct, the undiscovered intermediate forms being called "missing links."
The term was first used in a scientific context by [[Charles Lyell]] in the third edition (1851) of his book ''Elements of Geology'' in relation to missing parts of the [[Geologic time scale|geological column]], but it was popularized in its present meaning by its appearance on page xi of his book ''[[Geological Evidences of the Antiquity of Man]]'' of 1863. By that time, it was generally thought that the end of the [[last glacial period]] marked the first appearance of humanity, but; Lyell drew on new findings in his ''Antiquity of Man'' to put the origin of human beings much further back in the deep geological past. Lyell wrote that it remained a profound mystery how the huge gulf between man and beast could be bridged.<ref>{{cite journal |last=Bynum |first=William F. |date=Summer 1984 |title=Charles Lyell's ''Antiquity of Man'' and its critics |journal=Journal of the History of Biology |volume=17 |issue=2 |pages=153–187 |doi=10.1007/BF00143731 |jstor=4330890 |s2cid=84588890 |issn=0022-5010 |ref=harv}}</ref> Lyell's vivid writing fired the public imagination, inspiring [[Jules Verne]]'s ''[[Journey to the Center of the Earth]]'' (1864) and [[Louis Figuier]]'s 1867 second edition of ''La Terre avant le déluge'' ("Earth before the Flood"), which included dramatic illustrations of savage men and women wearing animal skins and wielding stone axes, in place of the [[Garden of Eden]] shown in the 1863 edition.{{sfn|Browne|2003|pp=130, 218, 515}}
The idea of a "missing link" between humans and so-called "lower" animals remains lodged in the public imagination.<ref name="hm">{{cite web |url=http://www.biologytimes.com/why-the-term-missing-links-is-inappropriate/ |title=Why the term 'missing links' is inappropriate |last=Sambrani |first=Nagraj |date=10 June 2009 |website=Biology Times |type=Blog |accessdate=2015-05-19}}</ref> The search for a fossil showing transitional traits between apes and humans, however, was fruitless until the young Dutch geologist [[Eugène Dubois]] found a skullcap, a molar and a [[femur]] on the banks of [[Solo River]], [[Java]] in 1891. The find combined a low, ape-like [[skull roof]] with a brain estimated at around 1000 cc, midway between that of a chimpanzee and an adult human. The single molar was larger than any modern human tooth, but the femur was long and straight, with a knee angle showing that "[[Java Man]]" had walked upright.<ref>{{harvnb|Swisher|Curtis|Lewin|2001}}</ref> Given the name ''[[Homo erectus|Pithecanthropus erectus]]'' ("erect ape-man"), it became the first in what is now a long [[list of human evolution fossils]]. At the time it was hailed by many as the "missing link," helping set the term as primarily used for human fossils, though it is sometimes used for other intermediates, like the dinosaur-bird intermediary ''[[Archaeopteryx]]''.<ref>{{harvnb|Reader|2011}}</ref><ref>{{cite web |last=Benton |first=Michael J. |authorlink=Michael Benton |date=March 2001 |title=Evidence of Evolutionary Transitions |url=http://www.actionbioscience.org/evolution/benton2.html |website=[[actionbioscience]] |publisher=[[American Institute of Biological Sciences]] |___location=Washington, D.C. |accessdate=2012-03-29}}</ref>
[[File:Punctuated Equilibrium.svg|thumb|upright=1.7|Sudden jumps with apparent gaps in the fossil record have been used as evidence for [[punctuated equilibrium]]. Such jumps can be explained either by [[macromutation]] or simply by relatively rapid episodes of gradual evolution by natural selection, since a period of say 10,000 years barely registers in the fossil record.]]
While "Missingmissing link" is still a popular term, well -recognized by the public and often used in the popular media.,<ref name="zimmer">{{cite journal |last=Zimmer |first=Carl |authorlink=Carl Zimmer |date=19 May 2009 |title=Darwinius: It delivers a pizza, and it lengthens, and it strengthens, and it finds that slipper that's been at large under the chaise lounge [sic] for several weeks... |url=http://blogs.discovermagazine.com/loom/2009/05/19/darwinius-it-delivers-a-pizza-and-it-lengthens-and-it-strengthens-and-it-finds-that-slipper-thats-been-at-large-under-the-chaise-lounge-for-several-weeks/ |journal=[[Discover (magazine)|The Loom]] |type=Blog |___location=Waukesha, WI |publisher=[[Kalmbach Publishing]] |accessdate=2011-09-10}}</ref> Itthe term is, however, avoided in the scientific press,publications.<ref asname="NS2645" it/> relatesSome to the concept of the great chain of being and to the notion of simple organisms being primitive versions of complex ones, both of whichbloggers have beencalled discardedit in biology."inappropriate";<ref name="NS2645hm" />{{cite In any case,web |url=http://www.biologytimes.com/why-the -term itself -missing-links-is-inappropriate/ misleading,|title=Why asthe anyterm known'missing transitional fossil, like Java Man,links' is noinappropriate longer|last=Sambrani missing.|first=Nagraj While|date=10 eachJune find2009 will|website=Biology giveTimes rise|type=Blog to|accessdate=2015-05-19}}</ref> newboth gaps inbecause the evolutionarylinks storyare onno eachlonger side"missing", theand discoverybecause ofhuman moreevolution andis moreno transitional fossilslonger continuesbelieved to addhave tooccurred ourin knowledgeterms of evolutionarya single linear transitionsprogression.<ref name="NS2645" /><ref name="nomorelink">{{cite news |author=<!--Staff writer(s); no by-line.--> |title=Newly found fossils could link to human ancestor |url=http://www.cbc.ca/news/technology/newly-found-fossils-could-link-to-human-ancestor-1.930070 |work=[[CBC News]] |___location=Ottawa, Ontario, Canada |publisher=[[Canadian Broadcasting Corporation]] |date=8 April 2010 |accessdate=2015-05-19 |quote=It's tempting to call the new species a 'missing link' between earlier species and modern humans, but scientists say the concept no longer applies, given new knowledge of human evolution. [...] Researchers now say the evolution of humans consisted of a number of diverse species in many branches, not a single smooth line from ape-like species to humans.}}</ref>
===Punctuated equilibrium===
{{main|Punctuated equilibrium}}
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