Jessica Green is co-founder of phylogeny that is building a microbial map of the world.

杰西卡·格林是名为" 系统发育" 组织的联合创始人，该组织正在绘制一张微生物世界地图。

So using observations and the molecular clock approach, we can decide which traits will help us group animals into clades, or a group with all the descendants of the same common ancestor, and fit those clades together into a phylogeny.

因此，通过观察和方法，我们可以决定哪些特征可以帮助我们归类动物到化枝，或者把所有同一共同祖先的后代归为一类，这些化枝就这样集合在一起形成化树了。

And, in this tree, time moves from the root of the tree to the tips of the branches, meaning that branches towards the bottom of the phylogeny diverged before the branches at the top.

在这棵树上，时间从树根向树枝顶端移动，这意味着系统发育底的树枝比顶的树枝先化。

Here is a phylogeny of the land plants that are alive today.

这是现存陆地植物的系统发育图。

So zoologists will often make several phylogenies using different approaches.

所以，动物学家通常会使用不同的方法来化树。

In a phylogeny, individual species or groups of species sit at the tips of the tree.

在化树中，单个物种或一组物种群位于树的顶端。

There's no best way to make a phylogeny, and one phylogeny is really just a hypothesis for all the evolutionary relationships between species or clades based on specific traits or groups of traits.

没有最好的方法来化树，一棵化树也只是一个假设而已，根据具体的性状或广泛的性状来对所有种群和化枝之间的化关系做假设。

Using the maximum likelihood approach, we'd end up with a phylogeny where the sequence of events has the highest probability.

使用最大似然方法，我们可以得出序列事件在化树有最高的可能性。

So, as zoologists using maximum parsimony, we'd choose the phylogeny that shows feathers evolving once.

所以，当动物学家使用最大简约法时，我们选择羽毛只化一次的化树。

Keeping track of who's related to who can get messy, so we study animal relationships using a diagram called a phylogeny or a phylogenetic tree.

记录谁与谁是有关系的会变得很混乱，因此我们利用一个图示来研究物的关系，那就是系统发生树，或化树。

Orion Zaks at Tel Aviv University and her colleagues study vertebrate phylogeny and neuroanatomy.

奥里昂·扎克斯在特拉维夫大学与她的同事研究脊椎动物的系统发生学和神经解剖学。

There are many organisms out there whose phylogeny is a total mystery to us.

有许多生物的系统发育对我们来说完全是个谜。

The across phylogeny, and you ask, which is, by the way, a fascinating topic, at some point, we should do a separate podcast on sleep across different species, because I know like me, you love, you know, the whole variety of species.

在不同物种之间，这个问题非常有趣，我们以后应该专门做一个关于不同物种睡眠的播客，因为我知道像我一样，你也喜欢了解各种各样的物种。

And I think now, you know, it'd be nice to, there've been a couple of papers that have sort of integrated phylogeny and environmental stuff, you know, very, very elegantly.

我认为现在如果能将系统发育和环境因素巧妙地结合起来，那会很棒。已经有几篇论文在这方面做得相当出色。

And so if we trace the phylogeny of a tapulasaurus, what we would find is each of these points here represents a common ancestor of the dinosaurs above it.

因此， 如果我们追溯塔普拉萨龙的系统发育，我们会发现， 这里的每一个点都代表其上方恐龙的一个共同祖先。

Think about the brain and we can move back across the complexity of phylogeny from humans to mammals to birds to reptiles, amphibians, fish, bacteria, whatever you want.

想象一下大脑， 我们可以从人类回溯到哺乳动物、鸟类、爬行动物、两栖动物、鱼类，甚至细菌， 跨越整个生物化谱系的复杂性。

And our goal is that the phylogeny will match taxonomy.

我们的目标是系统发育与类学相匹配。

This is just the concept of phylogeny, right?

这只是系统发育的概念，对吧？

And at the time, you know, there was the Joe Felsenstein's, you know, independent contrasts and a lot of studies looking at phylogeny.

当时， 乔·费尔斯通（Joe Felsenstein）提出的独对比法，以及许多专注于系统发育的研究， 都是学界的热点。

So, let's go to the phylogeny.

因此，接下来让我们看看化树。