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恐竜の爬虫類の目をクローズ アップ

新しい研究により、視覚遠近法として知られる、最初に遮られた場所へ誰かの視線を追う能力は、哺乳類が出現する約6000万年前に恐竜の系統に起源がある可能性が高いことが明らかになった。 この認知能力は特定の鳥類で発見されており、鳥類の恐竜や鳥類は哺乳類で同様の能力が出現する以前から顕著な神経認知を持っていたことを示唆しています。

ルンド大学の研究者らは、視覚的な遠近法、つまり遮られた視線を追う認知能力が、哺乳類に出現する約6000万年前に恐竜の系統に起源があることを発見した。 この発見は、複雑な認知が主に哺乳類で進化したという概念に疑問を投げかけ、鳥とその祖先である恐竜の認知能力を浮き彫りにしました。

あなたの近くの誰かが環境内の何かに頭を向けると、あなたはおそらくその視線の方向を追わずにはいられないでしょう。 この反応は哺乳類、鳥類、さらには爬虫類でも同様に観察されます。 これは、他の方法では見逃してしまう可能性のある、仲間の注目を集めたものに関する情報を収集する効果的な方法です。 ただし、はるかに高度な行動は、最初は視界が遮られている場所まで誰かの視線を追うことです。 相手が何を見ているのかを確認するために自分の位置を変えることで、相手が異なる視点を持っていることを理解していることを示すことができます。 視覚的な遠近法として知られるこの能力は、1歳半から2歳の子供たちに発達し、後に言及的コミュニケーションや他人が自分とは異なる心を持っていることを理解するための基礎となります。

視覚的な視点の取得は、これまでのところ、ごく少数の分野でのみ発見されています。[{” attribute=””>species. Mainly in apes and some monkeys, but also in dogs and crow birds. However, there is limited knowledge regarding the evolutionary origins of this crucial social skill. A team of researchers from Lund University aimed to investigate a potential early emergence of visual perspective taking in dinosaurs. Through a comparison of alligators with the most primitive existing birds, known as palaeognaths, they discovered that visual perspective taking originated in the dinosaur lineage likely 60 million years, or more, prior to its appearance in mammals.

Dinosaur Gaze Following

Figure 1. Experimental setups of the study. Panels depict experiment setups (from left to right) for alligators, small birds (red junglefowl and elegant-crested tinamous), and large birds (emus and rheas). (A) Setups for experiment 1 (gazing up). (B) Setups for experiment 2 (gazing to the side). (C) Setups for experiment 3 (geometrical). Red dots depict stimuli used to lure demonstrators’ gazes (for more information about stimuli, see Materials and Methods). Credit: Science Advances, DOI: 10.1126/sciadv.adf0405


Crocodilians are the closest living relatives to birds. Their neuroanatomy has remained largely unchanged for hundreds of millions of years, and is similar to that of the common ancestor of dinosaurs and crocodilians. Palaeognath birds comprise the ostrich birds, such as emus and rheas, but also the flighted tinamous. Their brains are in large parts comparable to their forebearers, the non- avian paravian dinosaurs, which feature such celebrities as the velociraptors. Comparing these two groups of animals creates a bracket around the extinct lineage of dinosaurs leading up to modern birds.

The study revealed that alligators do not demonstrate visual perspective taking, although they do follow gaze to a visible location. In contrast, all tested bird species exhibited visual perspective taking. Additionally, the birds engaged in a behavior called “checking back,” where the observer looks back into the eyes of the gazer, and re-tracks the gaze, when unable to find anything in the direction of their gaze the first time. This behavior indicates an expectation that the gaze is referring to a target in the environment. Previously, this has only been observed in humans, apes and monkeys, and ravens.

Palaeognath birds emerged 110 million years ago, predating the two mammal groups endowed with visual perspective taking – primates and dogs – with 60 million years. Considering the neuroanatomical similarities between these birds and their non-avian forebearers, it is plausible that the skill originated even earlier in the dinosaur lineage. However, it is less likely to have been present among the earliest dinosaurs, which had more alligator-like brains. Maybe future research will show the ability to be more widespread among mammals than currently known, but even if that would be the case it will most probably still be predated by the dinosaur origin. Nevertheless, it is not surprising that visual perspective taking emerged earlier in the dinosaurs, which include the birds, given their superior vision compared to most mammals, that historically relied on nocturnal adaptations. It was only with the emergence of the primates and certain carnivores that our visual capabilities improved.

This is yet another finding that calls into question the prevailing view that mammals drove the evolution of complex cognition, and that they are the cognitive yardstick to which other animals should be compared. An increasing number of studies show the remarkable neurocognition of the avian dinosaurs, the birds, which might prompt a rethinking of the natural history of cognition.

Comments from the authors:

Senior author, prof. Mathias Osvath:

“Early in my career, crow birds earned the nickname “feathered apes,” due to numerous research findings that showcased their remarkable cognition. However, I’m beginning to question whether it would be more fitting to consider primates as honorary birds.”

First author (then PhD-student), Dr. Claudia Zeiträg:

“Birds are commonly being overlooked when it comes to their cognitive skills. Our findings show that they do not only have several cognitive skills on par with those of apes, but that their forebearers most likely had these skills long before they evolved in mammals.”

Middle author, Dr. Stephan Reber:

“Crocodilians are ideal models to study the evolutionary origins of cognitive capacities in birds. What they share most probably existed in the common ancestor of dinosaurs and crocodilians. If crocodilians lack an ability birds possess, it likely evolved in the dinosaur lineage after the split. This approach allows us to study the cognition of extinct species.”

Reference: “Gaze following in Archosauria—Alligators and palaeognath birds suggest dinosaur origin of visual perspective taking” by Claudia Zeiträg, Stephan A. Reber and Mathias Osvath, 19 May 2023, Science Advances.
DOI: 10.1126/sciadv.adf0405


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