When 哺乳動物s 現れるd from the dark: 絶滅 of dinosaurs 66 millions years ago 原因（となる）d creatures to begin living in daylight

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The enormous asteroid that struck the Earth 66 million years ago not only wiped out the dinosaurs, but 徹底的に changed the behaviour of 哺乳動物s.

A new 熟考する／考慮する has 設立する that 哺乳動物s only started 存在 active in the daytime after 非，不，無-avian dinosaurs were wiped out.

The findings 供給する 重要な insights into the changing behaviour of animals through history.

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A new 熟考する／考慮する has 設立する that 哺乳動物s only started 存在 active in the daytime after 非，不，無-avian dinosaurs were wiped out. The illustration is an artist's impression of Mesozoic animals 設立する fossilised in the Kayenta 激しく揺する fo rmation

研究員s from UCL and Tel Aviv University's Steinhardt Museum of Natural History have discovered when 哺乳動物s started living in the daytime for the first time.

The 研究員s analysed data of 2,415 種類 of 哺乳動物s alive today using computer algorithms to 再建する the likely activity of the 古代の ancestors who lived millions of years ago.

Two different mammalian family trees portraying 代案／選択肢 timelines for the 進化 of 哺乳動物s were used in the 分析.

Results showed that 哺乳動物s switched to daytime activity すぐに after the dinosaurs disappeared.

This change wasn't instantaneous ? it 伴う／関わるd an 中間の 行う／開催する／段階 of mixed day and night activity over millions of years.

Mr Roi Maor, lead author of the 熟考する／考慮する, said: 'We were very surprised to find such の近くに correlation between the 見えなくなる of dinosaurs and the beginning of daytime activity in 哺乳動物s, but we 設立する the same result 全員一致で using several 代案／選択肢 分析.'?

Activity pattern 配当s across the two models 見積（る）s mammalian 進化. 種類 activity patterns are denoted by different colours in the perimeter circle, where nocturnal is blue, diurnal is yellow, cathemeral is green and あいまいな is magenta

The team 設立する that the ancestors of simian 大主教s - 含むing gorillas, gibbons and tamarins - were の中で the first to give up nocturnal activity altogether.

But the two evolutionary timelines 変化させるd, giving a window between 52-33 million years ago for this to have occurred.

This 発見 fits 井戸／弁護士席 with the fact that simian 大主教s are the only 哺乳動物s that have 発展させるd adaptations to seeing 井戸／弁護士席 in daylight.

These 観察s led to the 開発 of the 'nocturnal bottleneck' theory.

This theory 示唆するs 早期に 哺乳動物s had to 制限する their activity to the night time to 避ける 衝突 with dinosaurs that were active by day.

When the dinosaurs died out 哺乳動物s were able to move into the newly 利用できる daytime niche.

Simians have 類似の visual acuity and colour perception as diurnal reptiles and birds ? groups that have always lived in the daytime.

Professor Kate Jones, co-author of the 熟考する／考慮する, said: 'It's very difficult to relate behaviour changes in 哺乳動物s that lived so long ago to 生態学の 条件s at the time, so we can't say that the dinosaurs dying out 原因（となる）d 哺乳動物s to start 存在 active in the daytime.

The 観察s led to the 開発 of the 'nocturnal bottleneck' theory. This theory 示唆するs 早期に 哺乳動物s had to 制限する their activity to the night time to 避ける 衝突 with dinosaurs that were active by day (在庫／株 image)

'However, we see a （疑いを）晴らす correlation in our findings.'

Professor Tamar Dayan, co-author of the 熟考する／考慮する, 追加するd: 'We analysed a lot of data on the behaviour and 家系 of living animals for two 推論する／理由s - firstly, because the 化石 記録，記録的な／記録する from that 時代 is very 限られた／立憲的な and secondly, behaviour as a trait is very hard to infer from 化石s.

'You have to 観察する a living 哺乳動物 to see if it is active at night or in the day.

WHAT HAPPENED WHEN THE ASTEROID HIT EARTH??

Within 10 hours of the 衝撃, a 大規模な 津波 waved ripped through the 湾 coast.

This 原因（となる）d 地震s and 地滑りs in areas as far as Argentina.?

The creatures living at the time were not just 苦しむing from the waves - the heat was much worse.

While 調査／捜査するing 'dooms day' 研究員s 設立する small 粒子s of 激しく揺する and other 破片 that was 発射 into the 空気／公表する when the asteroid 衝突，墜落d.

After the asteroid had 攻撃する，衝突する, the 研究員s believe that the Earth would have behaved like a 'slow-moving fluid'

Called spherules, these small 粒子s covered the world with a one-tenth インチ 厚い 層 of すす.

専門家s explain that losing the light from the sun 原因（となる）d a 完全にする 崩壊（する） in the aquatic system as the phytoplankton base of almost all aquatic food chains would have been 除去するd.

It's believed that the more than 180 million years of 進化 that brought the world to the Cretaceous point was destroyed in いっそう少なく than the lifetime of a Tyrannosaurus rex, which is about 20 to 30 years.?

宣伝

'化石 証拠 from 哺乳動物s often 示唆する that they were nocturnal even if they were not.

'Many その後の adaptations that 許す us to live in daylight are in our soft tissues.'

The team say その上の 研究 is needed to better understand the mammalian family tree to give more 正確な （警察などへの）密告，告訴（状） on when the behaviour of 種類 changes from night time to day time activity.