Did ancestors of mammals and insects that were using the same brain exist?

Recently the NHK News On-line reported the following:

哺乳類と昆虫 共通の脳を持つ祖先が存在か

11月4日 5時21分

ものを触ったときに感じる感覚、「触覚」が脳に伝わる神経回路の構造は、ヒトを含む哺乳類と昆虫とで共通しているとする研究成果を東京大学のグループが発表しました。聴覚や視覚など五感のうち４つではすでに共通の構造があることが判明していて、グループでは、今から６億年ほど前には、哺乳類と昆虫には、共通の脳を持つ祖先が存在していた可能性が高いとしています。

東京大学分子細胞生物学研究所の伊藤啓准教授らのグループは、大きさ２ミリほどのショウジョウバエを使ってものを触ったときに感じる「触覚」の情報が脳にどう伝わるのか調べました。

その結果、皮膚が押されたり、関節が曲がったりするのを感知する複数の神経がそれぞれ脳の違った場所に情報を伝えるなど哺乳類と昆虫とで神経回路の構造が共通していることがわかったということです。

視覚、嗅覚、味覚、聴覚、触覚の五感のうち、触覚を除く４つの感覚では、すでに哺乳類と昆虫とで神経回路の構造が共通しているとわかっていて今回の研究で五感すべてで共通点が見つかったことになります。

研究グループの伊藤准教授は、「およそ６億年前には、哺乳類と昆虫の共通の祖先がいて、五感を感じる脳を持っていた可能性が高い」と話しています。

My translation

A group from the University of Tokyo announced their study results which suggested that the sense to feel when touching a thing, and the structure of the neural circuit by which the "sense of touch" was transmitted to a brain in insect was common to mammals including human. It revealed that a common structure had already been confirmed in the four senses out of the five senses that included hearing and seeing; this group suggested that there was a high possibility for an ancestor with a brain common to both mammals and insects had existed about 600 million years ago.

A group consisting of Professor Ito Kei and others from the University of Tokyo molecule cellular biology research center used a drosophila of about 2 millimeters in size to examine how the signal of feeling on "sense of touch" was transmitted to a brain when touching a thing.

As a result, in sensing the feeling by pushing the skin and bending a joint, more than one nerve would hand down signals respectively to the different places in the brain in mammals and insects, and it was said that they found out that the structure of the neural circuit was the same.

In the five senses of sight, smell, palate, hearing and touching, with the exception for the sense of touching, all four senses had already showed that the structure of the neural circuit was the same in mammals and insects, and by this study a common point was found for all five senses.

Associate professor Ito of the study group said that “approximately 600 million years ago mammals and insects had a common ancestor, and the possibility that it had the brain that felt the five senses is high."

         This is an interesting observation. Thank you for the hard work of Professor Ito.