It is revealing to consider the etymologies of the words associated with sequential thinking. First, I must familiarize you with a term from linguistics: cognate. Two words in two different languages are cognate if they both derive from the same word in the common ancestral language of the two different languages. For example, consider father (English) and vater (German). These words are obviously closely related; they both derive from an earlier word. What might surprise you is that the ancestral language for this particular word was spoken about 5,000 years ago. The cognates for father extend across an amazing variety of languages: Latin (pater), French (), Greek (), Persian (), Sanskrit (), and Irish (). We can therefore conclude that the ancestral word for father was in use at least 5,000 years ago.
In the same way, we can discover a great many other words that were spoken in this ancestral language (which, by the way, is known as Proto-Indo-European). Some of these words are: mother, two, three, six, seven, eight, ewe, wagon, spy, ignite, equine, and agriculture. Of course, the words I have listed are the modern English cognates; the root words are quite different.
Not all words are common across all languages. For example, the words for copper, gold, and silver are rather different across these languages, because Proto-Indo-European was spoken before people began smelting these metals. By the time the Bronze Age had started, the descendents of the Proto-Indo-Europeans had spread all over Eurasia and were no longer in contact, so their languages evolved independently from that point forward. Thus, they all developed different words for gold, copper, and silver.
Language evolution didn’t stop once the Proto-Indo-Europeans split up. Every time a group of people spread out and lost contact with each other, their language started to evolve differently with each group, and eventually there were two separate languages. Thus, Proto-Indo-European broke up into a number of language families, such as Germanic, Celtic, and Italic. These languages later broke up into other languages: Germanic broke up into a northern form and a western form. The northern version eventually split up into Swedish, Norwegian, Danish, and Icelandic. The western version broke up into German, Dutch, and English. Thus, English has more cognates with German and Dutch than it has with Swedish and Danish.
This means that you can get a rough idea of when two languages separated by comparing the number of cognates they share. Some linguists have run wild with this idea, carrying out detailed statistical calculations based on the entire vocabularies of different languages in order to get more precise datings of the separations of languages. This field, called glottochronology, raises some eyebrows amid the more staid linguists.
But you can also turn this idea around to get a rough idea of when a word entered a language, or at least when it became regularly used. For example, our gold is aurum in Latin. Clearly, the words for gold entered the languages after the Italic branch, from which Latin is descended, separated from the Germanic branch. By looking for the extent to which cognates spread across different languages, we can get a rough idea of when they entered those languages.
Of course, the history of any single word is a tortuous path, and cognates can be made and lost for a hundred oddball reasons that would make such a dating scheme unreliable. For example, our word day is closer to Latin dies than German Tag. If English is closer to German than to Latin, how come this word is closer to Latin than to German? The answer lies in the screwy history of English. When William the Conqueror took over England, he brought in a bunch of French-speaking overlords who proceeded to impose some of their language on the Germanic-speaking natives. The resulting partial blend of German and French became English.
So we can’t place much weight on any single word. However, if we examine groups of related words, we can get more reliable results. I did that with a group of words that are all related to complex sequential reasoning: and, therefore, else, or, if, but, because, and perhaps. I then looked up their translations in fourteen other languages, looking for cognates. The results are presented here:
This diagram is rather difficult to interpret. Each color represents a single word, whose English version is near the right edge of the graph. Lines in that color represent cognate connections for that word. For example, the word for else in German is anders, and in Dutch it is ander. Clearly, English is the odd man out. Two out of three of the languages in that group have cognates, so we draw a line through the group in such a way as to link German and Dutch. English, however, gets its own version of the word, so its line is not connected with the German-Dutch line. In the same manner, the north Germanic languages have a two cognates for else. The Italic languages have a very common word for else, so their line is drawn much earlier. Lastly, the Celtic languages have no cognates, so their line is drawn after they have all separated from each other.
I must emphasize that any single word can be misleading. For example, if I had used otherwise instead of else, then English would have shared the cognate with Dutch and German (other and ander are considered to be close enough to count). So perhaps I placed the line for else too low. What’s important here is the overall pattern. All of these words except and and therefore appear to have entered their languages sometime between 500 AD and 1500 AD -- much later than many other words in the overall vocabularies. People weren’t using these words very much until after Rome fell. Note that these words are all central to verbal reasoning. Without them, you can’t do much verbal reasoning. Which in turn means that verbal reasoning was not widespread until well after 500 AD.