Editing Wallace Line (section)

== Historical context ==
[[File:Wallace-line1.jpg|thumb|upright=1.9|The original drawing of the line in Wallace's paper]]

One of the earliest descriptions of the biodiversity in the Indo-Australian Archipelago dates back to 1521 when Venetian explorer [[Antonio Pigafetta|Pigafetta]] recorded the biological contrasts between the Philippines and the [[Maluku Islands]] (Spice Islands) (on opposite sides of Wallace's Line) during the continuation of the voyage of [[Ferdinand Magellan]], after Magellan had been killed on [[Mactan]]. Later on, the English navigator [[George Windsor Earl|G.W. Earl]] published his observations in faunal differences between the islands in the Indo-Australian archipelago. 

In 1845, G.W. Earl described how shallow seas connected islands on the west ([[Sumatra]], [[Java]], etc.) with the Asian continent and with similar wildlife, and islands on the east such as [[New Guinea]] were connected to Australia and were characterized by the presence of [[marsupial]]s.<ref>{{cite book <!--it was a pamphlet-->|last=Earl |first=G.W. |author-link=George Windsor Earl |date=1845 |title=On the Physical Geography of South-Eastern Asia and Australia }}</ref>

These early investigations assisted Wallace in developing his theories about the biogeography which he stated publicly in his 1859 paper after extensively traveling the region.<ref name="Ali-Heaney-2021" /> He proposed a line to the east of [[Bali]] since "all the islands eastward of [[Borneo]] and [[Java]] formed part of an Australian or Pacific continent, from which they were separated."<ref name="Wallace-1863">{{harvnb|Wallace|1863|pp=217–234}}</ref>

The proposal of the line, however, was not the main objective of Wallace's endeavours: His primary purpose was in fact to understand the geological phenomena and the colonization events that caused the boundaries in faunal distribution in the region through the development of his theories of evolution and biogeography.<ref name="Ali-Heaney-2021" /> Wallace's studies in [[Indonesia]] demonstrated the emerging [[theory of evolution]], at about the same time as [[J.D. Hooker]] and [[Asa Gray]] published essays also supporting [[Charles Darwin|Darwin]]'s hypothesis.<ref>{{cite book |last=Bowler |first=P.J. |author-link=Peter J. Bowler |date=1989 |title=Evolution: The history of an idea |edition=Rev. |location=Berkeley, California |publisher=University of California Press |oclc=17841313 |isbn= 0-520-06385-6 |url= https://www.worldcat.org/oclc/17841313}}</ref> On the other hand, the lack of knowledge of [[tectonic plate]]s, and the uncertainty about biodiversity in the [[Philippines]], left Wallace with some contradicting points he had to deal with concerning his theory on biogeography.<ref name="Ali-Heaney-2021" /> 

In fact, Wallace did not include the Philippines in his 1859 paper, and the determination of a line in honor of his name was suggested by [[T.H. Huxley]] (1868).<ref>{{cite journal |last=Huxley |first=Thomas Henry |author-link=Thomas Henry Huxley |date=January 1868 |title=December 10, 1868 |journal=[[Proceedings of the Zoological Society of London]] |volume=36 |issue=1 |pages=622–637 |doi=10.1111/j.1469-7998.1868.tb00455.x |issn=0370-2774}}</ref><ref>{{cite journal |last=Camerini |first=J.R. |date= December 1993 |title=Evolution, biogeography, and maps: An early history of Wallace's line |journal=[[Isis (journal)|Isis]] |volume=84 |issue=4 |pages=700–727 |doi=10.1086/356637 |pmid=8307726 |s2cid=15219070 |issn=0021-1753 |url= https://www.journals.uchicago.edu/doi/10.1086/356637}}</ref> Huxley studied the distribution of [[gallinaceous birds]] in the archipelago, and noticed that species in the Philippines were remarkably distinct from those in the Asiatic realm. Based on that, he redrew Wallace's boundary placing it to the west of the Philippines and named it "Wallace's Line", although Wallace himself had refused to include the Philippines on the east side of the line.<ref name="Ali-Heaney-2021" />

Because of the complexity of the geographical landscape and the differences in diversity of organisms around the archipelago, continuous attempts to characterize faunal and botanical boundaries were carried out after Wallace. Some of them are

* [[Sclater]] line (1894)
* [[Richard Lydekker|Lydekker's]] line (1896)
* [[Paul Pelseneer|Pelseneer]]'s faunal balance (1904), also known as [[Max Carl Wilhelm Weber|Weber line]]<ref name="Pelseneer 1904">{{cite journal |last1=Pelseneer |first1=Paul |title=La ligne de Weber, limite zoologique de l'Asie et de l'Australie |journal=Bulletin de la Classe des Sciences Académie Royale de Belgique |date=1904 |volume=1904 |pages=1001–1022}}</ref>
* [[Ernst Mayr|Mayr]]'s faunal balance (1944)

In addition, several smaller transition sub-regional boundaries were also proposed.<ref name="Ali-Heaney-2021" />

More recent work assessing biodiversity assemblages, phylogeny, and using computer-based geospatial tools to analyze previous boundaries have led to patterns of division similar to those proposed through the 19th&nbsp;century, although some special cases not explained before are reinforced by these modern analyses.<ref name="Rueda-2013"> {{cite journal |author1=Rueda, M.|author2=Rodríguez, M. Á.|author3=Hawkins, B. A.|date=2013| title=Identifying global zoogeographical regions: lessons from Wallace|journal=Journal of Biogeography|volume=40|issue=12|pages=2215–2225|ref=Rueda}}</ref>

{{full citation|date=May 2023}} for instance, evaluated the distribution of land mammals, birds, and amphibians in Wallace's realms and concluded that the boundaries suggested by Wallace remain valid. Ali ''et al''. (2020), in a different attempt, studied the fauna of [[Christmas Island]] and indicated that most of the ancestral colonizers of the island's land mammals and amphibians disappeared from the [[Lombok Strait]]. Therefore, they propose a re-conformation of Wallace's Line so that Christmas Island would be sited on the Australasian side of the biogeographical divide, instead of the oriental side.<ref name="Ali-Heaney-2021" />