Genyornis

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Genyornis
Temporal range: Late Pleistocene
Genyornis BW.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Dromornithidae
Genus: Genyornis
Species: G. newtoni
Binomial name
Genyornis newtoni
Stirling & Zietz, 1896

Genyornis newtoni was a large, flightless bird that lived in Australia. Over two metres in height, they became extinct 50±5 thousand years ago. Many other species became extinct in Australia around that time, coinciding with the arrival of humans.

It is not clear to what degree Dromornithidae were carnivores. The massive, crushing beaks of at least of some species suggest that they were a combination of predators and scavengers, much like today's hyenas. Their closest living relatives are waterfowl.

Two main theories propose a cause for megafauna extinction - human impact and climate change. A study has been performed in which more than 700 Genyornis eggshell fragments were dated.[1] Through this, it was determined that Genyornis declined and became extinct over a short period—too short for it to be plausibly explained by climate change. The authors considered this to be a very good indication that the entire mass extinction event in Australia was due to human activity, rather than climate change. A 2015 study collected egg shell fragments of Genyornis from around 200 sites that show burn marks.[2] Analysis of amino acids in the egg shells showed a thermal gradient consistent with the egg being placed on an ember fire. The egg shells were dated to between 53.9 and 43.4 thousand years before present, suggesting that humans were collecting and cooking Genyornis eggs in the thousands of years before their extinction.

Characterizing blackened Genyornis eggshell. (a) Excavated variably burnt and unusually broken eggshell from the Wood Point site, Port Broughton, Spencer Gulf, SA (b) Eggshell fragment from region W, blackened only at one end, with locations of samples for amino-acid analysis. (c) Concentrations of the stable amino acids glutamic acid (Glu), valine (Val) and leucine (Leu) are reduced in direct proportion to the degree of visual blackening, with samples 3–6 exhibiting only slightly lower concentrations than in unheated fragments of the same egg; ±1σ uncertainties (7%) based on duplicate analyses. Unheated fragments of the same egg exhibit 10% inter-eggshell variability for the same amino acids (6 fragments analysed). Less stable amino acids show similar patterns.

However, there is a counter argument that suggests the pattern of long term extinctions of mega fauna as the climate became drier and more arid towards the Last Glacial Maximum, affecting primary vegetation types, may also have been a factor in Genyornis extinction.[3]

In May 2010, archaeologists announced the rediscovery of an Aboriginal rock art painting, possibly 40,000 years old, at the Nawarla Gabarnmung rock art site in the Northern Territory, that depicts two of the birds in detail.[4] Late survival of Genyornis in temperate south west Victoria has also recently been suggested, based on dateable Aboriginal traditions.[5]

References[edit]

  1. ^ Miller, G. H.; Magee, J. W.; Johnson, B. J.; Fogel, M. L.; Spooner, N. A.; McCulloch, M. T.; Ayliffe, L. K. (1999-01-08). "Pleistocene Extinction of Genyornis newtoni: Human Impact on Australian Megafauna". Science 283 (5399): 205–208. doi:10.1126/science.283.5399.205. PMID 9880249. 
  2. ^ Miller, Gifford; Magee, John; Smith, Mike; Spooner, Nigel; Baynes, Alexander; Lehman, Scott; Fogel, Marilyn; Johnston, Harvey; Williams, Doug; Clark, Peter; Florian, Christopher; Holst, Richard; DeVogel, Stephen (2016). "Human predation contributed to the extinction of the Australian megafaunal bird Genyornis newtoni ∼47 ka". Nature Communications 7: 10496. doi:10.1038/ncomms10496. ISSN 2041-1723. PMID 26823193. 
  3. ^ Wroe, Stephen; Field, Judith (2006). "A review of the evidence for a human role in the extinction of Australian megafauna and an alternative interpretation". Quaternary Science Reviews 25 (21–22): 2692. doi:10.1016/j.quascirev.2006.03.005. 
  4. ^ "Megafauna cave painting could be 40,000 years old". www.abc.net.au. 2010-05-31. Retrieved 2010-05-31. ; Gunn, R. C. et al. "What bird is that?" Australian Archaeology 73(2011):1-12.
  5. ^ Rupert Gerritsen (2011) Beyond the Frontier: Explorations in Ethnohistory, Canberra: Batavia Online Publishing. pp.52-69 ISBN 978-0-9872141-4-0