What did rats evolve from?
All rodents are placental mammals of the order Rodentia that fall under the subclass Eutheria (birth-giving mammals) under the class Mammalia of the Animal Kingdom.
All rats are rodents because they fall under the order Rodentia under the subclass Eutheria all under the class Mammalia of the Animal Kingdom.
Rodents evolved from ancestors that were also kind of placental mammals of subclass Eutheria somewhere around 66 million years ago.
So, rats being a type of rodents had evolved from some ancestral placental rodents somewhere after 66 million years ago as estimated from some found-out fossil rodents.
Some researchers say that it was near about 45 million years ago that the present-day rats had evolved from their ancestral rodent species.
Nevertheless, all of the species of rodents and species of rats share the same common ancestor which was a kind of placental mammal, but the time leading to evolution varied significantly.
Meaning that, as documented by fossil records the evolutionary history can be stated like that, previously rodents had evolved from a kind of ancestral placental mammal around 66 million years ago, and later during the 45 million years ago time period rats evolved from an ancestral species of rodents.
So yes, the earliest record of such evolution comes from the mid-Paleocene geographical epoch to the Late Paleocene Epoch time period, and this was all during that time period when the non-avian dinosaurs just got extinct.
Such evolutionary concepts and statements were driven from the various fossil records found in Laurasia (the present-day regions of modern-day North America, Europe, and Asia).
How have rats evolved?
It was about 80 million years ago when humans and rodents separated from a common ancestor and followed different lineages. This was the time when evolution was seen to first occur in rodents.
Later on, it was around 66 million years ago when rodents had perfectly evolved from a kind of ancestral placental mammal which was also a kind of partial rodent as seen from fossil records.
Sooner or later, it was around 45 million years ago when the evolution of rats had started from a common ancestral rodent species.
And, it was during the time period between 12 and 24 million years ago when rats and mice started diverging into two different families and followed different lineages.
It has been estimated through fossil records that it was something around 18 million years ago when significant evolutionary changes became noticeable in rodents. This was when rats had perfectly evolved from a common ancestral rodent species.
And, around 12 million years ago, rats and mice had perfectly diverged into different lineages forming two different families of their own.
We all know that there are four forces of evolution: mutation, gene flow, genetic drift, and natural selection. Same here in the case of rats as well these evolutionary forces had driven significant evolutionary changes.
Scientists today say that rodents and in fact all rats have evolved over time from early Eutherians (placental mammals) which then included the vast majority of all living mammals.
And, that the slow initiation of evolution in rodents had started somewhere around 145 million years ago.
And that, it was after 66 million years ago when the significant evolutionary changes became noticeable in rodents.
And, that it was after 45 million years ago when the significant evolutionary changes became partially noticeable in rats, and after 18 million years ago when various significant evolutionary changes became perfectly noticeable in rats.
However, due to the lack of proper solid pieces of evidence like fossil records, etc., the evolutionary studies of rats and overall the Rodents above the familial level have become a continuing long or arduous search.
And that researchers have no clear-cut idea and theories in order to clarify exactly how and where the eutherian mammals originated, and how from them rodents and rats had evolved all due to lack of proper evolutionary pieces of evidence.
Where did rats originally come from?
Researchers say that the ancestors of rats originally come from Asia and Australia where they first originated about 18 million years ago, but are now found all over the world in different varieties of species.
Stereotypical rats of the genus Rattus were native to the Mediterranean and Asian countries. So, they are believed to have originated from parts of the Middle East, India, China, Japan, and Southeast Asia (including the Philipines, New Guinea, and Australia).
The famous species of rats known as the Black Rat (Rattus rattus) originally come from Asia (mostly from the Indo-Malayan region and major parts of India), and later it had slowly spread into the European countries more than 5,000 to 10,000 years ago.
The Brown Rat is also known as the Sewer rat or Norway rat, and it had first originated in parts of Europe and America and had later spread to parts of Australia.
Many Norway Rat species have also originated on the plains of Asia, probably in what is now known as northern China and Mongolia.
There are some Brown Rat species as well, that originated from China, and now can be seen in many parts of Europe, India, America, and Africa.
Did rats evolve from mice?
Mice had evolved from rats. Many researchers believe that it was anywhere between 12 and 24 million years ago when rats and mice started diverging into two different families and ancestral lineages from an ancestral species of rat.
Many believe that mice had evolved from an ancestral species of rat and it was clearly noticeable only after 12 million years ago. The various evolutionary forces had a great impact in causing such evolution.
The ancestral species of rats were also a kind of rodent-like mammals that used to move hurriedly with short quick steps along the surface of the earth as determined by some fossil records but not guaranteed due to lack of strong pieces of evidence.
Even the study of the rat genome by 20 different institutions from six different countries has s showcased that rats didn’t evolve from mice but mice did evolve from rats.
But, it is very much interesting to note that the past and also the present pace of evolution in rats is much more rapid than that in the case of mice.
Do rats and mice share a common ancestor?
Yes, rats and mice share a common ancestor which was a rodent-like mammal that move hurriedly along the surface of the earth some 65 million years ago as shown through the various phylogenetic and palaeontological records.
And as already mentioned above, that it was only between 12 and 24 million years ago when rats and mice started diverging into two different lineages from that rodent-like common ancestor.
As per the genomic data, it has been also seen that rat and mice genomes are almost similar due to their common ancestry, with rats having approximately 2.75 billion base pairs while mice having approximately 2.6 billion base pairs.
It is to be also noted that all mammals have occurred from a common mammalian non-ave like dinosaur following significant evolution.
Later on, rodents started evolving from a partially rodent-like mammalian ancestor following various evolutionary pressures.
And sooner or later, it was from a complete rodent-like mammalian ancestor from which rats have evolved, and from a complete rat-like mammalian ancestor mice started evolving.
This all indicates that both rats and mice share a common ancestor, and due to the various evolutionary pressures, they started diverging into separate lineages.
Whatever may be the cause, it is very much important here to note that evolutionary change has occurred at a faster rate in rodents than in primates over the course of millions of years of subsequent evolution.
Do rats and humans have a common ancestor?
Yes, both rats and humans are mammals and so yes they have a common ancestor. At present, similarities in DNA and other genomic structures and their functionalities between the two (humans and rats) provide much strong evidence to support this statement.
Rats belong to Order Rodentia of Class Mammalia of the Animal Kingdom, while Humans belong to Order Primates of Class Mammalia of the Animal Kingdom. Yes, both are mammals and had a common mammalian ancestor in their lineages.
Various books of evolution state that all mammals including humans and rats had evolved somewhere close to 300 million years ago from amniotes called Synapsids.
Synapsids (includes mammals and every animal more closely related to mammals) is now a fossil organism of a Permian and Triassic group (300 million years ago), the members of which show increasingly mammalian characteristics and include the ancestors of mammals.
And, it was during the Paleogene period (something around 34 million years ago) when Rapid evolution and diversification of placental mammals took place.
Genomic analysis has also shown that both rats and humans have a matching genome that relates to their common ancestry.
It has been noticed that there are something about absolutely necessary 280 large blocks of chromosomes that appear to be virtually identical in both rats and humans.
It is to be noted here that approximately one-fourth (1/4th) of the human genome is shared with both rats and mice, and this 1/4th portion consists of about approximately 700 megabases of DNA matter.