Original photo courtesy of Ryan Somma. This file is licensed under the Creative Commons.
Macrauchenia was a camel-like animal deriving its name from Auchenia, meaning “big neck” in Greek, and its first remains, which date back 7 million years, were found in South America, primarily in Argentina (1). Macrauchenia was a herbivore with its distinctive feature being the nostrils that opened on top of its head, similar to whales. This morphologically unusual animal baffled Charles Darwin for a long time, who had failed to place it in the proper evolutionary context. “It was a fairly bulky quadruped, probably not very fleet of foot,” said Ross MacPhee, a curator at the American Museum of Natural History and a co-author on the recently published study on Macrauchenia (2). He further added, “its outstanding feature, however, was its nose.”
It has been well established over time that ancient DNA (aDNA) sequencing is a powerful tool for uncovering phylogenetic relationships of extinct animals and observing evolution in real time. In the past, attempts to place Macrauchenia on the tree of life were initially based on bone morphology and later focused on using ancient collagen. In the new study, led by MacPhee and co-author, Hofreiter, they extend a 2015 collagen study (3) by extracting mitochondrial DNA from a fossil found in South America. The existing protein results were corroborated and new mitogenomic data was generated using an advanced aDNA alignment approach to recover a near-complete mitochondrial genome of this mysterious animal.
In this new study, the authors carried out genetic analyses on 6 Macrauchenia fossils originating from various sites in the southern part of South America. Successful DNA recovery was made possible using a modified protocol with QIAGEN’s MinElute silica spin columns. DNA libraries were constructed using a single-strand library building approach, specifically developed for highly degraded ancient samples. Furthermore, the amplified libraries were cleaned up using a MinElute PCR Purification Kit following QIAGEN’s protocol.
A promising southernmost Macrauchenia DNA sample, MAC002, was further considered for validation using deep sequencing, followed by mitochondrial genome reconstruction. A phylogenetic tree reconstruction based on the mitogenome data finally helped secure a place for Macrauchenia as a sister taxon to the order Perissodactyla, but close to the radiation of major lineages within the superorder Laurasiatheria (4).
It is fascinating how ancient DNA and protein samples from extinct species can provide insights into the history of life on Earth and help us understand evolution better.
You can continue reading about this interesting study in Nature Communications at www.nature.com/articles/ncomms15951.
- 1. https://en.wikipedia.org/wiki/Macrauchenia
- 2. http://edition.cnn.com/2017/06/27/world/extinct-animal-ungulate-macrauchenia-darwin-tree-of-life/index.html
- 3. Welker, F. et al. Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates. Nature 522, 81–84 (2015). https://www.ncbi.nlm.nih.gov/pubmed/25799987
- 4. Westbury, M. et al. A mitogenomic timetree for Darwin’s enigmatic South American mammal Macrauchenia patachonica. Commun. 8, 15951 (2017). https://www.nature.com/articles/ncomms15951