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So researchers have wondered about the evolution of male parenting behavior in birds for quite some time.
研究者一直都很好奇，鳥類的雄性育兒行為都是怎樣進化而來的。
And now there's research showing that for some of the birds' dinosaur relatives, it's likely that the male parent was also in charge of taking care of the eggs.
現在有研究證明，對鳥類的一些恐龍親戚來說，很可能是父方負責照料恐龍蛋。
How did they figure that out?
他們怎么發現的？
Well, first they looked at clutch volume, that's the number of eggs in the nest of crocodiles, birds and three types of dinosaurs, including Oviraptors that are thought to be closely related to the dinosaur ancestors of birds.
首先他們從產卵數入手，也就是鱷魚、鳥類和三種被認為與鳥類的恐龍祖先關系非常密切的恐龍（包括竊蛋龍）窩里有多少蛋。
So when researchers examined fossilized remains of nests, they found that the dinosaurs had larger clutch volumes, more eggs in the nests that is, than most of the crocodiles and birds that were studied.
當研究人員檢驗這些窩巢里的化石遺跡時，他們發現恐龍的產卵數更大，也就是說，在窩里有更多的蛋，比研究內大多數鱷魚和鳥類都多。
But, and this is important, their clutch volumes matched those of birds that have only male parental care.
但（這點很重要）它們的產卵數和鳥類中只有父方撫養幼兒的數量是吻合的。
You see, bird species in which only the males take care of the nest tend to have the largest clutches of eggs.
鳥類中，只有父方照顧幼兒的鳥往往有最多的蛋。
So what's the connection between bird and dinosaur behavior?
那么，鳥類和恐龍的行為之間有什么聯系呢？
Well, researchers now believe, because of this study, that the male parenting behavior of these birds might have its origins in the behavior of dinosaurs.
由于這個研究，研究人員現在相信，鳥類中的父方育兒行為可能源自恐龍行為。
Based only on evidence of clutch volume size, the number of eggs?
證據只有產卵數嗎，即蛋的數量？
No, there's more.
還有更多證據。
They also examined the fossilized bones of those three types of dinosaurs that were found on or near nests to determine their sex.
他們還檢驗了這三種在窩巢上或旁邊發現的恐龍化石，來確定恐龍性別。
You see, adult female birds during egg production produce a layer of spongy bone tissue inside certain long bones.
成年的雌鳥在產卵時會在某些長骨中分泌一層海綿狀的骨組織。
And so did female dinosaurs of the kinds that were investigated.
所調查的雌雄恐龍中也是這樣的。
This spongy tissue serves as a source of calcium for eggshell formation.
這層海綿組織是為蛋殼的形成提供鈣質的。
But when the dinosaur fossils were examined, there were no spongy bone deposits, meaning that those dinosaurs on the nests were probably adult males who wouldn't have needed calcium for making eggshells.
但人們在檢驗恐龍化石時，沒有發現任何海綿骨沉淀。也就是說，這些在窩里的恐龍很可能是成年雄性恐龍，它們不需要形成蛋殼所需的鈣質。
Exactly. And then there's this: birds like the kiwi, the ostrich and the emu; they share certain physical characteristics with these dinosaurs.
正確。還有：像幾維鳥、鴕鳥和鴯鹋鳥的這些鳥類，與這些恐龍有著相同的生理特征。
And interestingly, they also show a consistent pattern of nest care by the male.
有趣的是，它們也表現出一貫的父方育兒的模式。
